diff --git a/lib/box/file.ts b/lib/box/file.ts
index 99bb509ddd..30d71cdddf 100644
--- a/lib/box/file.ts
+++ b/lib/box/file.ts
@@ -19,12 +19,12 @@ class File {
     this.type = type;
   }
 
-  read(options?: ReadFileOptions): Promise<string | Buffer> {
-    return readFile(this.source, options);
+  read(options?: ReadFileOptions): Promise<string> {
+    return readFile(this.source, options) as Promise<string>;
   }
 
-  readSync(options?: ReadFileOptions): string | Buffer {
-    return readFileSync(this.source, options);
+  readSync(options?: ReadFileOptions): string {
+    return readFileSync(this.source, options) as string;
   }
 
   stat(): Promise<fs.Stats> {
diff --git a/lib/box/index.ts b/lib/box/index.ts
index 3222b55880..e55079c8de 100644
--- a/lib/box/index.ts
+++ b/lib/box/index.ts
@@ -7,12 +7,13 @@ import { magenta } from 'picocolors';
 import { EventEmitter } from 'events';
 import { isMatch, makeRe } from 'micromatch';
 import type Hexo from '../hexo';
+import type { NodeJSLikeCallback } from '../types';
 
 const defaultPattern = new Pattern(() => ({}));
 
 interface Processor {
   pattern: Pattern;
-  process: (file: File) => void;
+  process: (file?: File) => any;
 }
 
 class Box extends EventEmitter {
diff --git a/lib/extend/console.ts b/lib/extend/console.ts
index a5b7868af9..0c32af063c 100644
--- a/lib/extend/console.ts
+++ b/lib/extend/console.ts
@@ -1,5 +1,6 @@
 import Promise from 'bluebird';
 import abbrev from 'abbrev';
+import type { NodeJSLikeCallback } from '../types';
 
 type Option = Partial<{
   usage: string;
@@ -19,7 +20,7 @@ interface Args {
   _: string[];
   [key: string]: string | boolean | string[];
 }
-type AnyFn = (args: Args) => any;
+type AnyFn = (args: Args, callback?: NodeJSLikeCallback<any>) => any;
 interface StoreFunction extends AnyFn {
   desc?: string;
   options?: Option;
@@ -29,7 +30,7 @@ interface Store {
   [key: string]: StoreFunction
 }
 interface Alias {
-  [key: string]: string
+  [abbreviation: string]: string
 }
 
 class Console {
diff --git a/lib/extend/deployer.ts b/lib/extend/deployer.ts
index ae88664cdc..5014433c4e 100644
--- a/lib/extend/deployer.ts
+++ b/lib/extend/deployer.ts
@@ -1,10 +1,11 @@
 import Promise from 'bluebird';
+import type { NodeJSLikeCallback } from '../types';
 
 interface StoreFunction {
   (deployArg: {
     type: string;
     [key: string]: any
-  }) : any;
+  }, callback?: NodeJSLikeCallback<any>) : any;
 }
 interface Store {
   [key: string]: StoreFunction
diff --git a/lib/extend/filter.ts b/lib/extend/filter.ts
index 2af06fae87..98b34de1f3 100644
--- a/lib/extend/filter.ts
+++ b/lib/extend/filter.ts
@@ -11,6 +11,7 @@ interface FilterOptions {
   args?: any[];
 }
 
+
 interface StoreFunction {
   (data?: any, ...args: any[]): any;
   priority?: number;
@@ -75,7 +76,7 @@ class Filter {
     if (index !== -1) list.splice(index, 1);
   }
 
-  exec(type: string, data: any[], options: FilterOptions = {}): Promise<any> {
+  exec(type: string, data: any, options: FilterOptions = {}): Promise<any> {
     const filters = this.list(type);
     if (filters.length === 0) return Promise.resolve(data);
 
@@ -90,7 +91,7 @@ class Filter {
     })).then(() => args[0]);
   }
 
-  execSync(type: string, data: any[], options: FilterOptions = {}) {
+  execSync(type: string, data: any, options: FilterOptions = {}) {
     const filters = this.list(type);
     const filtersLen = filters.length;
     if (filtersLen === 0) return data;
diff --git a/lib/extend/generator.ts b/lib/extend/generator.ts
index 2854f8f869..125d2d3de9 100644
--- a/lib/extend/generator.ts
+++ b/lib/extend/generator.ts
@@ -1,4 +1,5 @@
 import Promise from 'bluebird';
+import type { NodeJSLikeCallback } from '../types';
 
 interface BaseObj {
   path: string;
@@ -9,7 +10,7 @@ type ReturnType = BaseObj | BaseObj[];
 type GeneratorReturnType = ReturnType | Promise<ReturnType>;
 
 interface GeneratorFunction {
-  (locals: object): GeneratorReturnType;
+  (locals: object, callback?: NodeJSLikeCallback<any>): GeneratorReturnType;
 }
 
 type StoreFunctionReturn = Promise<ReturnType>;
diff --git a/lib/extend/migrator.ts b/lib/extend/migrator.ts
index 5ab0f7063e..ce5ae77544 100644
--- a/lib/extend/migrator.ts
+++ b/lib/extend/migrator.ts
@@ -1,6 +1,8 @@
 import Promise from 'bluebird';
+import type { NodeJSLikeCallback } from '../types';
+
 interface StoreFunction {
-  (args: any): any
+  (args: any, callback?: NodeJSLikeCallback<any>): any
 }
 
 interface Store {
diff --git a/lib/extend/renderer.ts b/lib/extend/renderer.ts
index 15f90c6de6..530b071e18 100644
--- a/lib/extend/renderer.ts
+++ b/lib/extend/renderer.ts
@@ -1,5 +1,6 @@
 import { extname } from 'path';
 import Promise from 'bluebird';
+import type { NodeJSLikeCallback } from '../types';
 
 const getExtname = (str: string) => {
   if (typeof str !== 'string') return '';
@@ -13,7 +14,7 @@ export interface StoreFunctionData {
   text?: string;
   engine?: string;
   toString?: any;
-  onRenderEnd?: any;
+  onRenderEnd?: (...args: any[]) => any;
 }
 
 export interface StoreSyncFunction {
@@ -21,7 +22,7 @@ export interface StoreSyncFunction {
   (
     data: StoreFunctionData,
     options: object,
-    // callback: NodeJSLikeCallback<string>
+    // callback?: NodeJSLikeCallback<string>
   ): any;
   output?: string;
   compile?: (local: object) => any;
@@ -30,6 +31,7 @@ export interface StoreFunction {
   (
     data: StoreFunctionData,
     options: object,
+    callback?: NodeJSLikeCallback<any>
   ): Promise<any>;
   (
     data: StoreFunctionData,
@@ -57,7 +59,7 @@ class Renderer {
     this.storeSync = {};
   }
 
-  list(sync: boolean): Store | SyncStore {
+  list(sync = false): Store | SyncStore {
     return sync ? this.storeSync : this.store;
   }
 
@@ -97,7 +99,6 @@ class Renderer {
       this.storeSync[name].output = output;
 
       this.store[name] = Promise.method(fn);
-      // eslint-disable-next-line no-extra-parens
       this.store[name].disableNunjucks = (fn as StoreFunction).disableNunjucks;
     } else {
       if (fn.length > 2) fn = Promise.promisify(fn);
diff --git a/lib/extend/tag.ts b/lib/extend/tag.ts
index d44b5dd993..b9648d3297 100644
--- a/lib/extend/tag.ts
+++ b/lib/extend/tag.ts
@@ -2,12 +2,14 @@ import { stripIndent } from 'hexo-util';
 import { cyan, magenta, red, bold } from 'picocolors';
 import { Environment } from 'nunjucks';
 import Promise from 'bluebird';
+import type { NodeJSLikeCallback } from '../types';
+
 const rSwigRawFullBlock = /{% *raw *%}/;
 const rCodeTag = /<code[^<>]*>[\s\S]+?<\/code>/g;
 const escapeSwigTag = (str: string) => str.replace(/{/g, '&#123;').replace(/}/g, '&#125;');
 
 interface TagFunction {
-  (args: any[], content: string): string;
+  (args: any[], content: string, callback?: NodeJSLikeCallback<any>): string | PromiseLike<string>;
 }
 interface AsyncTagFunction {
   (args: any[], content: string): Promise<string>;
@@ -251,14 +253,17 @@ class Tag {
     if (env.hasExtension(name)) env.removeExtension(name);
   }
 
-  render(str: string, options: { source?: string } = {}, callback?: NodeJSLikeCallback<any>): Promise<any> {
+  render(str: string): Promise<any>;
+  render(str: string, callback: NodeJSLikeCallback<any>): Promise<any>;
+  render(str: string, options: { source?: string, [key: string]: any }, callback?: NodeJSLikeCallback<any>): Promise<any>;
+  render(str: string, options: { source?: string, [key: string]: any } | NodeJSLikeCallback<any> = {}, callback?: NodeJSLikeCallback<any>): Promise<any> {
     if (!callback && typeof options === 'function') {
       callback = options;
       options = {};
     }
 
     // Get path of post from source
-    const { source = '' } = options;
+    const { source = '' } = options as { source?: string };
 
     return Promise.fromCallback(cb => {
       this.env.renderString(
diff --git a/lib/hexo/default_config.ts b/lib/hexo/default_config.ts
index 5e01f5781d..bea0921ddd 100644
--- a/lib/hexo/default_config.ts
+++ b/lib/hexo/default_config.ts
@@ -46,7 +46,9 @@ export = {
     wrap: true,
     exclude_languages: [],
     language_attr: false,
-    hljs: false
+    hljs: false,
+    line_threshold: 0,
+    first_line_number: 'always1'
   },
   prismjs: {
     preprocess: true,
diff --git a/lib/hexo/index.ts b/lib/hexo/index.ts
index abd2b05387..2da92f6b90 100644
--- a/lib/hexo/index.ts
+++ b/lib/hexo/index.ts
@@ -7,7 +7,7 @@ import { EventEmitter } from 'events';
 import { readFile } from 'hexo-fs';
 import Module from 'module';
 import { runInThisContext } from 'vm';
-const {version} = require('../../package.json');
+const { version } = require('../../package.json');
 import logger from 'hexo-log';
 
 import {
@@ -37,6 +37,8 @@ import loadDatabase from './load_database';
 import multiConfigPath from './multi_config_path';
 import { deepMerge, full_url_for } from 'hexo-util';
 import type Box from '../box';
+import type { AssetGenerator, LocalsType, NodeJSLikeCallback, NormalPageGenerator, NormalPostGenerator, PageGenerator, PostGenerator, SiteLocals } from '../types';
+
 let resolveSync; // = require('resolve');
 
 const libDir = dirname(__dirname);
@@ -48,7 +50,8 @@ const routeCache = new WeakMap();
 
 const castArray = (obj: any) => { return Array.isArray(obj) ? obj : [obj]; };
 
-const mergeCtxThemeConfig = ctx => {
+// eslint-disable-next-line no-use-before-define
+const mergeCtxThemeConfig = (ctx: Hexo) => {
   // Merge hexo.config.theme_config into hexo.theme.config before post rendering & generating
   // config.theme_config has "_config.[theme].yml" merged in load_theme_config.js
   if (ctx.config.theme_config) {
@@ -56,11 +59,12 @@ const mergeCtxThemeConfig = ctx => {
   }
 };
 
-const createLoadThemeRoute = function(generatorResult, locals, ctx) {
+// eslint-disable-next-line no-use-before-define
+const createLoadThemeRoute = function(generatorResult: NormalPageGenerator | NormalPostGenerator, locals: LocalsType, ctx: Hexo) {
   const { log, theme } = ctx;
   const { path, cache: useCache } = locals;
 
-  const layout = [...new Set(castArray(generatorResult.layout))];
+  const layout: string[] = [...new Set(castArray(generatorResult.layout))];
   const layoutLength = layout.length;
 
   // always use cache in fragment_cache
@@ -94,7 +98,7 @@ const createLoadThemeRoute = function(generatorResult, locals, ctx) {
   };
 };
 
-function debounce(func: () => void, wait: number) {
+function debounce(func: () => void, wait: number): () => void {
   let timeout: NodeJS.Timeout;
   return function() {
     clearTimeout(timeout);
@@ -105,12 +109,15 @@ function debounce(func: () => void, wait: number) {
 }
 
 interface Args {
-  debug?: any;
-  safe?: any;
-  silent?: any;
-  _?: any[];
-  output?: any;
-  config?: any;
+  debug?: boolean;
+  safe?: boolean;
+  silent?: boolean;
+  draft?: boolean;
+  drafts?: boolean;
+  _?: string[];
+  output?: string;
+  config?: string;
+  [key: string]: any;
 }
 
 interface Query {
@@ -132,6 +139,17 @@ interface Extend {
   tag: Tag
 }
 
+interface Env {
+  args: Args;
+  debug: boolean;
+  safe: boolean;
+  silent: boolean;
+  env: string;
+  version: string;
+  cmd: string;
+  init: boolean;
+}
+
 type DefaultConfigType = typeof defaultConfig;
 interface Config extends DefaultConfigType {
   [key: string]: any;
@@ -236,7 +254,7 @@ class Hexo extends EventEmitter {
   public scaffold_dir: string;
   public theme_dir: string;
   public theme_script_dir: string;
-  public env: any;
+  public env: Env;
   public extend: Extend;
   public config: Config;
   public log: ReturnType<typeof logger>;
@@ -253,16 +271,6 @@ class Hexo extends EventEmitter {
   public locals: Locals;
   public version: string;
   public _watchBox: () => void;
-  public page: any;
-  public path: any;
-  public url: any;
-  public layout: any;
-  public view_dir: any;
-  public site: any;
-  public args: any;
-  public cache: any;
-  public alias: any;
-  public data: any;
   public lib_dir: string;
   public core_dir: string;
   static lib_dir: string;
@@ -348,7 +356,7 @@ class Hexo extends EventEmitter {
     this._bindLocals();
   }
 
-  _bindLocals() {
+  _bindLocals(): void {
     const db = this.database;
     const { locals } = this;
 
@@ -391,7 +399,7 @@ class Hexo extends EventEmitter {
     });
   }
 
-  init() {
+  init(): Promise<void> {
     this.log.debug('Hexo version: %s', magenta(this.version));
     this.log.debug('Working directory: %s', magenta(tildify(this.base_dir)));
 
@@ -418,15 +426,16 @@ class Hexo extends EventEmitter {
     });
   }
 
-  call(name: string, args: any, callback?: NodeJSLikeCallback<any>) {
+  call(name: string, callback?: NodeJSLikeCallback<any>): Promise<any>;
+  call(name: string, args: object, callback?: NodeJSLikeCallback<any>): Promise<any>;
+  call(name: string, args?: object | NodeJSLikeCallback<any>, callback?: NodeJSLikeCallback<any>): Promise<any> {
     if (!callback && typeof args === 'function') {
-      callback = args;
+      callback = args as NodeJSLikeCallback<any>;
       args = {};
     }
 
     const c = this.extend.console.get(name);
 
-    // eslint-disable-next-line no-extra-parens
     if (c) return (Reflect.apply(c, this, [args]) as any).asCallback(callback);
     return Promise.reject(new Error(`Console \`${name}\` has not been registered yet!`));
   }
@@ -435,7 +444,7 @@ class Hexo extends EventEmitter {
     return this.database.model(name, schema);
   }
 
-  resolvePlugin(name: string, basedir: string) {
+  resolvePlugin(name: string, basedir: string): string {
     try {
       // Try to resolve the plugin with the Node.js's built-in require.resolve.
       return require.resolve(name, { paths: [basedir] });
@@ -453,9 +462,9 @@ class Hexo extends EventEmitter {
     }
   }
 
-  loadPlugin(path: string, callback?: NodeJSLikeCallback<any>) {
+  loadPlugin(path: string, callback?: NodeJSLikeCallback<any>): Promise<any> {
     return readFile(path).then(script => {
-      // Based on: https://github.com/joyent/node/blob/v0.10.33/src/node.js#L516
+      // Based on: https://github.com/nodejs/node-v0.x-archive/blob/v0.10.33/src/node.js#L516
       const module = new Module(path);
       module.filename = path;
       module.paths = Module._nodeModulePaths(path);
@@ -478,12 +487,12 @@ class Hexo extends EventEmitter {
     }).asCallback(callback);
   }
 
-  _showDrafts() {
+  _showDrafts(): boolean {
     const { args } = this.env;
     return args.draft || args.drafts || this.config.render_drafts;
   }
 
-  load(callback?: NodeJSLikeCallback<any>) {
+  load(callback?: NodeJSLikeCallback<any>): Promise<any> {
     return loadDatabase(this).then(() => {
       this.log.info('Start processing');
 
@@ -497,7 +506,7 @@ class Hexo extends EventEmitter {
     }).asCallback(callback);
   }
 
-  watch(callback?: NodeJSLikeCallback<any>) {
+  watch(callback?: NodeJSLikeCallback<any>): Promise<any> {
     let useCache = false;
     const { cache } = Object.assign({
       cache: false
@@ -530,7 +539,7 @@ class Hexo extends EventEmitter {
     }).asCallback(callback);
   }
 
-  unwatch() {
+  unwatch(): void {
     if (this._watchBox != null) {
       this.source.removeListener('processAfter', this._watchBox);
       this.theme.removeListener('processAfter', this._watchBox);
@@ -545,12 +554,10 @@ class Hexo extends EventEmitter {
   _generateLocals() {
     const { config, env, theme, theme_dir } = this;
     const ctx = { config: { url: this.config.url } };
-    const localsObj = this.locals.toObject();
+    const localsObj = this.locals.toObject() as SiteLocals;
 
     class Locals {
-      page: {
-        path: string;
-      };
+      page: NormalPageGenerator | NormalPostGenerator;
       path: string;
       url: string;
       config: object;
@@ -558,10 +565,10 @@ class Hexo extends EventEmitter {
       layout: string;
       env: any;
       view_dir: string;
-      site: object;
+      site: SiteLocals;
       cache?: boolean;
 
-      constructor(path: string, locals) {
+      constructor(path: string, locals: NormalPageGenerator | NormalPostGenerator) {
         this.page = { ...locals };
         if (this.page.path == null) this.page.path = path;
         this.path = path;
@@ -578,9 +585,9 @@ class Hexo extends EventEmitter {
     return Locals;
   }
 
-  _runGenerators() {
+  _runGenerators(): Promise<(AssetGenerator | PostGenerator | PageGenerator)[]> {
     this.locals.invalidate();
-    const siteLocals = this.locals.toObject();
+    const siteLocals = this.locals.toObject() as SiteLocals;
     const generators = this.extend.generator.list();
     const { log } = this;
 
@@ -595,17 +602,19 @@ class Hexo extends EventEmitter {
     }, []);
   }
 
-  _routerRefresh(runningGenerators: Promise<any[]>, useCache: boolean) {
+  _routerRefresh(runningGenerators: Promise<(AssetGenerator | PostGenerator | PageGenerator)[]>, useCache: boolean): Promise<void> {
     const { route } = this;
     const routeList = route.list();
     const Locals = this._generateLocals();
     Locals.prototype.cache = useCache;
 
-    return runningGenerators.map(generatorResult => {
+    return runningGenerators.map((generatorResult: AssetGenerator | PostGenerator | PageGenerator) => {
       if (typeof generatorResult !== 'object' || generatorResult.path == null) return undefined;
 
       // add Route
       const path = route.format(generatorResult.path);
+      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+      // @ts-ignore
       const { data, layout } = generatorResult;
 
       if (!layout) {
@@ -613,8 +622,8 @@ class Hexo extends EventEmitter {
         return path;
       }
 
-      return this.execFilter('template_locals', new Locals(path, data), { context: this })
-        .then(locals => { route.set(path, createLoadThemeRoute(generatorResult, locals, this)); })
+      return this.execFilter('template_locals', new Locals(path, data as unknown as NormalPageGenerator | NormalPostGenerator), { context: this })
+        .then(locals => { route.set(path, createLoadThemeRoute(generatorResult as NormalPageGenerator | NormalPostGenerator, locals, this)); })
         .thenReturn(path);
     }).then(newRouteList => {
       // Remove old routes
@@ -628,7 +637,7 @@ class Hexo extends EventEmitter {
     });
   }
 
-  _generate(options: { cache?: boolean } = {}) {
+  _generate(options: { cache?: boolean } = {}): Promise<any> {
     if (this._isGenerating) return;
 
     const useCache = options.cache;
@@ -649,7 +658,7 @@ class Hexo extends EventEmitter {
       });
   }
 
-  exit(err) {
+  exit(err: Error): Promise<void> {
     if (err) {
       this.log.fatal(
         { err },
diff --git a/lib/hexo/load_config.ts b/lib/hexo/load_config.ts
index 489f4e03ff..009aa4587c 100644
--- a/lib/hexo/load_config.ts
+++ b/lib/hexo/load_config.ts
@@ -8,7 +8,7 @@ import { deepMerge } from 'hexo-util';
 import validateConfig from './validate_config';
 import type Hexo from './index';
 
-export = async (ctx: Hexo) => {
+export = async (ctx: Hexo): Promise<void> => {
   if (!ctx.env.init) return;
 
   const baseDir = ctx.base_dir;
@@ -53,7 +53,7 @@ export = async (ctx: Hexo) => {
   const themeDirFromNodeModules = join(ctx.plugin_dir, 'hexo-theme-' + theme) + sep; // base_dir/node_modules/hexo-theme-[config.theme]/
 
   // themeDirFromThemes has higher priority than themeDirFromNodeModules
-  let ignored = [];
+  let ignored: string[] = [];
   if (await exists(themeDirFromThemes)) {
     ctx.theme_dir = themeDirFromThemes;
     ignored = ['**/themes/*/node_modules/**', '**/themes/*/.git/**'];
@@ -66,7 +66,7 @@ export = async (ctx: Hexo) => {
 
 };
 
-async function findConfigPath(path: string) {
+async function findConfigPath(path: string): Promise<string> {
   const { dir, name } = parse(path);
 
   const files = await readdir(dir);
diff --git a/lib/hexo/load_database.ts b/lib/hexo/load_database.ts
index f0ac5decb0..f816a6f0ea 100644
--- a/lib/hexo/load_database.ts
+++ b/lib/hexo/load_database.ts
@@ -2,7 +2,7 @@ import { exists, unlink } from 'hexo-fs';
 import Promise from 'bluebird';
 import type Hexo from './index';
 
-export = (ctx: Hexo) => {
+export = (ctx: Hexo): Promise<void> => {
   if (ctx._dbLoaded) return Promise.resolve();
 
   const db = ctx.database;
diff --git a/lib/hexo/load_plugins.ts b/lib/hexo/load_plugins.ts
index 289474f00f..49802f9292 100644
--- a/lib/hexo/load_plugins.ts
+++ b/lib/hexo/load_plugins.ts
@@ -4,13 +4,13 @@ import Promise from 'bluebird';
 import { magenta } from 'picocolors';
 import type Hexo from './index';
 
-export = (ctx: Hexo) => {
+export = (ctx: Hexo): Promise<void[][]> => {
   if (!ctx.env.init || ctx.env.safe) return;
 
   return loadModules(ctx).then(() => loadScripts(ctx));
 };
 
-function loadModuleList(ctx: Hexo, basedir: string) {
+function loadModuleList(ctx: Hexo, basedir: string): Promise<any> {
   const packagePath = join(basedir, 'package.json');
 
   // Make sure package.json exists
diff --git a/lib/hexo/load_theme_config.ts b/lib/hexo/load_theme_config.ts
index 54c700960a..11056504aa 100644
--- a/lib/hexo/load_theme_config.ts
+++ b/lib/hexo/load_theme_config.ts
@@ -4,8 +4,9 @@ import { exists, readdir } from 'hexo-fs';
 import { magenta } from 'picocolors';
 import { deepMerge } from 'hexo-util';
 import type Hexo from './index';
+import type Promise from 'bluebird';
 
-export = (ctx: Hexo) => {
+export = (ctx: Hexo): Promise<void> => {
   if (!ctx.env.init) return;
   if (!ctx.config.theme) return;
 
@@ -31,7 +32,7 @@ export = (ctx: Hexo) => {
   });
 };
 
-function findConfigPath(path: string) {
+function findConfigPath(path: string): Promise<string> {
   const { dir, name } = parse(path);
 
   return readdir(dir).then(files => {
diff --git a/lib/hexo/locals.ts b/lib/hexo/locals.ts
index 7153cb0a48..ef3b51eb27 100644
--- a/lib/hexo/locals.ts
+++ b/lib/hexo/locals.ts
@@ -20,7 +20,7 @@ class Locals {
     });
   }
 
-  set(name: string, value: any) {
+  set(name: string, value: any): this {
     if (typeof name !== 'string') throw new TypeError('name must be a string!');
     if (value == null) throw new TypeError('value is required!');
 
@@ -32,7 +32,7 @@ class Locals {
     return this;
   }
 
-  remove(name: string) {
+  remove(name: string): this {
     if (typeof name !== 'string') throw new TypeError('name must be a string!');
 
     this.getters[name] = null;
@@ -41,7 +41,7 @@ class Locals {
     return this;
   }
 
-  invalidate() {
+  invalidate(): this {
     this.cache.flush();
 
     return this;
diff --git a/lib/hexo/multi_config_path.ts b/lib/hexo/multi_config_path.ts
index 7402657e90..27c9babd78 100644
--- a/lib/hexo/multi_config_path.ts
+++ b/lib/hexo/multi_config_path.ts
@@ -4,7 +4,7 @@ import yml from 'js-yaml';
 import { deepMerge } from 'hexo-util';
 import type Hexo from './index';
 
-export = (ctx: Hexo) => function multiConfigPath(base: string, configPaths: string, outputDir: string) {
+export = (ctx: Hexo) => function multiConfigPath(base: string, configPaths: string, outputDir: string): string {
   const { log } = ctx;
   const defaultPath = join(base, '_config.yml');
 
@@ -43,7 +43,7 @@ export = (ctx: Hexo) => function multiConfigPath(base: string, configPaths: stri
     }
 
     // files read synchronously to ensure proper overwrite order
-    const file = readFileSync(configPath);
+    const file = readFileSync(configPath) as string;
     const ext = extname(paths[i]).toLowerCase();
 
     if (ext === '.yml') {
diff --git a/lib/hexo/post.ts b/lib/hexo/post.ts
index f9269484e2..b7ecf3e988 100644
--- a/lib/hexo/post.ts
+++ b/lib/hexo/post.ts
@@ -8,6 +8,8 @@ import { slugize, escapeRegExp } from 'hexo-util';
 import { copyDir, exists, listDir, mkdirs, readFile, rmdir, unlink, writeFile } from 'hexo-fs';
 import { parse as yfmParse, split as yfmSplit, stringify as yfmStringify } from 'hexo-front-matter';
 import type Hexo from './index';
+import type { NodeJSLikeCallback, RenderData } from '../types';
+
 const preservedKeys = ['title', 'slug', 'path', 'layout', 'date', 'content'];
 
 const rHexoPostRenderEscape = /<hexoPostRenderCodeBlock>([\s\S]+?)<\/hexoPostRenderCodeBlock>/g;
@@ -224,14 +226,6 @@ interface Result {
   content?: string;
 }
 
-interface Data {
-  engine?: string;
-  content?: string;
-  disableNunjucks?: boolean;
-  markdown?: object;
-  source?: string;
-}
-
 interface PostData {
   title?: string;
   layout?: string;
@@ -388,7 +382,7 @@ class Post {
     }).thenReturn(result).asCallback(callback);
   }
 
-  render(source: string, data: Data = {}, callback?: NodeJSLikeCallback<never>) {
+  render(source: string, data: RenderData = {}, callback?: NodeJSLikeCallback<never>) {
     const ctx = this.context;
     const { config } = ctx;
     const { tag } = ctx.extend;
diff --git a/lib/hexo/register_models.ts b/lib/hexo/register_models.ts
index 88a73e6081..f6bb39b3ae 100644
--- a/lib/hexo/register_models.ts
+++ b/lib/hexo/register_models.ts
@@ -1,7 +1,7 @@
 import * as models from '../models';
 import type Hexo from './index';
 
-export = (ctx: Hexo) => {
+export = (ctx: Hexo): void => {
   const db = ctx.database;
 
   const keys = Object.keys(models);
diff --git a/lib/hexo/render.ts b/lib/hexo/render.ts
index 4d1ebda922..91ce8e01ff 100644
--- a/lib/hexo/render.ts
+++ b/lib/hexo/render.ts
@@ -3,16 +3,17 @@ import Promise from 'bluebird';
 import { readFile, readFileSync } from 'hexo-fs';
 import type Hexo from './index';
 import type { Renderer } from '../extend';
-import type { StoreFunctionData } from '../extend/renderer';
+import type { StoreFunction, StoreFunctionData, StoreSyncFunction } from '../extend/renderer';
+import { NodeJSLikeCallback } from '../types';
 
-const getExtname = (str: string) => {
+const getExtname = (str: string): string => {
   if (typeof str !== 'string') return '';
 
   const ext = extname(str);
   return ext.startsWith('.') ? ext.slice(1) : ext;
 };
 
-const toString = (result, options) => {
+const toString = (result: any, options: StoreFunctionData) => {
   if (!Object.prototype.hasOwnProperty.call(options, 'toString') || typeof result === 'string') return result;
 
   if (typeof options.toString === 'function') {
@@ -35,27 +36,27 @@ class Render {
     this.renderer = ctx.extend.renderer;
   }
 
-  isRenderable(path: string) {
+  isRenderable(path: string): boolean {
     return this.renderer.isRenderable(path);
   }
 
-  isRenderableSync(path: string) {
+  isRenderableSync(path: string): boolean {
     return this.renderer.isRenderableSync(path);
   }
 
-  getOutput(path: string) {
+  getOutput(path: string): string {
     return this.renderer.getOutput(path);
   }
 
-  getRenderer(ext: string, sync?: boolean) {
+  getRenderer(ext: string, sync?: boolean): StoreSyncFunction | StoreFunction {
     return this.renderer.get(ext, sync);
   }
 
-  getRendererSync(ext: string) {
+  getRendererSync(ext: string): StoreSyncFunction | StoreFunction {
     return this.getRenderer(ext, true);
   }
 
-  render(data: StoreFunctionData, options?: { highlight?: boolean; }, callback?: undefined) {
+  render(data: StoreFunctionData, options?: { highlight?: boolean; }, callback?: NodeJSLikeCallback<any>): Promise<any> {
     if (!callback && typeof options === 'function') {
       callback = options;
       options = {};
@@ -64,7 +65,7 @@ class Render {
     const ctx = this.context;
     let ext = '';
 
-    let promise;
+    let promise: Promise<string>;
 
     if (!data) return Promise.reject(new TypeError('No input file or string!'));
 
@@ -73,7 +74,7 @@ class Render {
     } else if (!data.path) {
       return Promise.reject(new TypeError('No input file or string!'));
     } else {
-      promise = readFile(data.path);
+      promise = readFile(data.path) as Promise<string>;
     }
 
     return promise.then(text => {
@@ -99,7 +100,7 @@ class Render {
     }).asCallback(callback);
   }
 
-  renderSync(data: StoreFunctionData, options = {}) {
+  renderSync(data: StoreFunctionData, options = {}): any {
     if (!data) throw new TypeError('No input file or string!');
 
     const ctx = this.context;
diff --git a/lib/hexo/router.ts b/lib/hexo/router.ts
index 33edb61478..8d9965e483 100644
--- a/lib/hexo/router.ts
+++ b/lib/hexo/router.ts
@@ -17,7 +17,7 @@ declare module 'stream' {
 class RouteStream extends Readable {
   public _data: any;
   public _ended: boolean;
-  public modified: any;
+  public modified: boolean;
 
   constructor(data: Data) {
     super({ objectMode: true });
@@ -28,7 +28,7 @@ class RouteStream extends Readable {
   }
 
   // Assume we only accept Buffer, plain object, or string
-  _toBuffer(data) {
+  _toBuffer(data: Buffer | object | string): Buffer | null {
     if (data instanceof Buffer) {
       return data;
     }
@@ -41,7 +41,7 @@ class RouteStream extends Readable {
     return null;
   }
 
-  _read() {
+  _read(): boolean {
     const data = this._data;
 
     if (typeof data !== 'function') {
@@ -84,7 +84,7 @@ class RouteStream extends Readable {
   }
 }
 
-const _format = (path: string) => {
+const _format = (path: string): string => {
   path = path || '';
   if (typeof path !== 'string') throw new TypeError('path must be a string!');
 
@@ -113,16 +113,16 @@ class Router extends EventEmitter {
     this.routes = {};
   }
 
-  list() {
+  list(): string[] {
     const { routes } = this;
     return Object.keys(routes).filter(key => routes[key]);
   }
 
-  format(path: string) {
+  format(path: string): string {
     return _format(path);
   }
 
-  get(path: string) {
+  get(path: string): RouteStream {
     if (typeof path !== 'string') throw new TypeError('path must be a string!');
 
     const data = this.routes[this.format(path)];
@@ -131,14 +131,14 @@ class Router extends EventEmitter {
     return new RouteStream(data);
   }
 
-  isModified(path: string) {
+  isModified(path: string): boolean {
     if (typeof path !== 'string') throw new TypeError('path must be a string!');
 
     const data = this.routes[this.format(path)];
     return data ? data.modified : false;
   }
 
-  set(path: string, data: any) {
+  set(path: string, data: any): this {
     if (typeof path !== 'string') throw new TypeError('path must be a string!');
     if (data == null) throw new TypeError('data is required!');
 
@@ -173,7 +173,7 @@ class Router extends EventEmitter {
     return this;
   }
 
-  remove(path: string) {
+  remove(path: string): this {
     if (typeof path !== 'string') throw new TypeError('path must be a string!');
     path = this.format(path);
 
diff --git a/lib/hexo/scaffold.ts b/lib/hexo/scaffold.ts
index 37b6e65e86..8b97c6305f 100644
--- a/lib/hexo/scaffold.ts
+++ b/lib/hexo/scaffold.ts
@@ -1,10 +1,15 @@
 import { extname, join } from 'path';
 import { exists, listDir, readFile, unlink, writeFile } from 'hexo-fs';
 import type Hexo from './index';
+import type { NodeJSLikeCallback } from '../types';
+import type Promise from 'bluebird';
+
 class Scaffold {
   public context: Hexo;
   public scaffoldDir: string;
-  public defaults: any;
+  public defaults: {
+    normal: string
+  };
 
   constructor(context: Hexo) {
     this.context = context;
@@ -21,7 +26,10 @@ class Scaffold {
     };
   }
 
-  _listDir() {
+  _listDir(): Promise<{
+    name: string;
+    path: string;
+  }[]> {
     const { scaffoldDir } = this;
 
     return exists(scaffoldDir).then(exist => {
@@ -36,11 +44,14 @@ class Scaffold {
     }));
   }
 
-  _getScaffold(name: string) {
+  _getScaffold(name: string): Promise<{
+    name: string;
+    path: string;
+  }> {
     return this._listDir().then(list => list.find(item => item.name === name));
   }
 
-  get(name: string, callback?: NodeJSLikeCallback<any>) {
+  get(name: string, callback?: NodeJSLikeCallback<any>): Promise<string> {
     return this._getScaffold(name).then(item => {
       if (item) {
         return readFile(item.path);
@@ -50,7 +61,7 @@ class Scaffold {
     }).asCallback(callback);
   }
 
-  set(name: string, content: any, callback: NodeJSLikeCallback<void>) {
+  set(name: string, content: any, callback?: NodeJSLikeCallback<void>): Promise<void> {
     const { scaffoldDir } = this;
 
     return this._getScaffold(name).then(item => {
@@ -61,7 +72,7 @@ class Scaffold {
     }).asCallback(callback);
   }
 
-  remove(name: string, callback: NodeJSLikeCallback<void>) {
+  remove(name: string, callback?: NodeJSLikeCallback<void>): Promise<void> {
     return this._getScaffold(name).then(item => {
       if (!item) return;
 
diff --git a/lib/hexo/update_package.ts b/lib/hexo/update_package.ts
index 4b8f3593bd..7913a67f67 100644
--- a/lib/hexo/update_package.ts
+++ b/lib/hexo/update_package.ts
@@ -1,8 +1,9 @@
 import { join } from 'path';
 import { writeFile, exists, readFile } from 'hexo-fs';
 import type Hexo from './index';
+import type Promise from 'bluebird';
 
-export = (ctx: Hexo) => {
+export = (ctx: Hexo): Promise<void> => {
   const pkgPath = join(ctx.base_dir, 'package.json');
 
   return readPkg(pkgPath).then(pkg => {
@@ -19,7 +20,7 @@ export = (ctx: Hexo) => {
   });
 };
 
-function readPkg(path: string) {
+function readPkg(path: string): Promise<any> {
   return exists(path).then(exist => {
     if (!exist) return;
 
diff --git a/lib/hexo/validate_config.ts b/lib/hexo/validate_config.ts
index 66af8ceeba..c7ca6477bd 100644
--- a/lib/hexo/validate_config.ts
+++ b/lib/hexo/validate_config.ts
@@ -1,6 +1,6 @@
 import type Hexo from './index';
 
-export = (ctx: Hexo) => {
+export = (ctx: Hexo): void => {
   const { config, log } = ctx;
 
   log.info('Validating config');
diff --git a/lib/models/types/moment.ts b/lib/models/types/moment.ts
index 59a86e1479..121be86248 100644
--- a/lib/models/types/moment.ts
+++ b/lib/models/types/moment.ts
@@ -1,12 +1,13 @@
 import warehouse from 'warehouse';
 import { moment, toMomentLocale } from '../../plugins/helper/date';
 
-declare module 'moment' {
-  export default interface Moment extends moment.Moment {
-    _d: Date;
-  // eslint-disable-next-line semi
-  }
-}
+// It'll pollute the moment module.
+// declare module 'moment' {
+//   export default interface Moment extends moment.Moment {
+//     _d: Date;
+//   // eslint-disable-next-line semi
+//   }
+// }
 
 class SchemaTypeMoment extends warehouse.SchemaType<moment.Moment> {
   public options: any;
@@ -90,7 +91,7 @@ class SchemaTypeMoment extends warehouse.SchemaType<moment.Moment> {
 function toMoment(value) {
   // FIXME: Something is wrong when using a moment instance. I try to get the
   // original date object and create a new moment object again.
-  if (moment.isMoment(value)) return moment(value._d);
+  if (moment.isMoment(value)) return moment((value as any)._d);
   return moment(value);
 }
 
diff --git a/lib/plugins/console/config.ts b/lib/plugins/console/config.ts
index 777bc4e1d0..c46f9793f3 100644
--- a/lib/plugins/console/config.ts
+++ b/lib/plugins/console/config.ts
@@ -4,7 +4,12 @@ import { extname } from 'path';
 import Promise from 'bluebird';
 import type Hexo from '../../hexo';
 
-function configConsole(this: Hexo, args): Promise<void> {
+interface ConfigArgs {
+  _: string[]
+  [key: string]: any
+}
+
+function configConsole(this: Hexo, args: ConfigArgs): Promise<void> {
   const key = args._[0];
   let value = args._[1];
 
diff --git a/lib/plugins/console/deploy.ts b/lib/plugins/console/deploy.ts
index 1da54819d4..811be33b48 100644
--- a/lib/plugins/console/deploy.ts
+++ b/lib/plugins/console/deploy.ts
@@ -2,7 +2,14 @@ import { exists } from 'hexo-fs';
 import { underline, magenta } from 'picocolors';
 import type Hexo from '../../hexo';
 
-function deployConsole(this: Hexo, args) {
+interface DeployArgs {
+  _?: string[]
+  g?: boolean
+  generate?: boolean
+  [key: string]: any
+}
+
+function deployConsole(this: Hexo, args: DeployArgs) {
   let config = this.config.deploy;
   const deployers = this.extend.deployer.list();
 
@@ -18,10 +25,6 @@ function deployConsole(this: Hexo, args) {
     return;
   }
 
-  const generateArgs = {...args};
-  generateArgs.d = false;
-  generateArgs.deploy = false;
-
   let promise;
 
   if (args.g || args.generate) {
diff --git a/lib/plugins/console/generate.ts b/lib/plugins/console/generate.ts
index c91b45e2d3..f6bfcd67a7 100644
--- a/lib/plugins/console/generate.ts
+++ b/lib/plugins/console/generate.ts
@@ -8,20 +8,32 @@ import { PassThrough } from 'stream';
 import { createSha1Hash } from 'hexo-util';
 import type Hexo from '../../hexo';
 
+interface GenerateArgs {
+  f?: boolean
+  force?: boolean
+  b?: boolean
+  bail?: boolean
+  c?: string
+  concurrency?: string
+  w?: boolean
+  watch?: boolean
+  d?: boolean
+  deploy?: boolean
+  [key: string]: any
+}
+
 class Generater {
   public context: Hexo;
-  public force: any;
-  public bail: any;
-  public concurrency: any;
-  public watch: any;
-  public deploy: any;
+  public force: boolean;
+  public bail: boolean;
+  public concurrency: string;
+  public watch: boolean;
+  public deploy: boolean;
   public generatingFiles: Set<any>;
   public start: [number, number];
-  public args: any;
-  public route: any;
-  public log: any;
+  public args: GenerateArgs;
 
-  constructor(ctx: Hexo, args) {
+  constructor(ctx: Hexo, args: GenerateArgs) {
     this.context = ctx;
     this.force = args.f || args.force;
     this.bail = args.b || args.bail;
@@ -193,7 +205,7 @@ class Generater {
   }
 }
 
-function generateConsole(args = {}) {
+function generateConsole(this: Hexo, args: GenerateArgs = {}) {
   const generator = new Generater(this, args);
 
   if (generator.watch) {
diff --git a/lib/plugins/console/list/index.ts b/lib/plugins/console/list/index.ts
index cd091ca272..f9b3cb4cd5 100644
--- a/lib/plugins/console/list/index.ts
+++ b/lib/plugins/console/list/index.ts
@@ -6,13 +6,17 @@ import tag from './tag';
 import category from './category';
 import type Hexo from '../../../hexo';
 
+interface ListArgs {
+  _: string[]
+}
+
 const store = {
   page, post, route, tag, category
 };
 
 const alias = abbrev(Object.keys(store));
 
-function listConsole(this: Hexo, args) {
+function listConsole(this: Hexo, args: ListArgs) {
   const type = args._.shift();
 
   // Display help message if user didn't input any arguments
diff --git a/lib/plugins/console/migrate.ts b/lib/plugins/console/migrate.ts
index afe5dfb537..d6b3ad3e47 100644
--- a/lib/plugins/console/migrate.ts
+++ b/lib/plugins/console/migrate.ts
@@ -1,7 +1,12 @@
 import { underline, magenta } from 'picocolors';
 import type Hexo from '../../hexo';
 
-function migrateConsole(this: Hexo, args) {
+interface MigrateArgs {
+  _: string[]
+  [key: string]: any
+}
+
+function migrateConsole(this: Hexo, args: MigrateArgs) {
   // Display help message if user didn't input any arguments
   if (!args._.length) {
     return this.call('help', {_: ['migrate']});
diff --git a/lib/plugins/console/new.ts b/lib/plugins/console/new.ts
index 64e3d83bd1..2b48b77b11 100644
--- a/lib/plugins/console/new.ts
+++ b/lib/plugins/console/new.ts
@@ -20,9 +20,20 @@ const reservedKeys = {
   silent: true
 };
 
-function newConsole(this: Hexo, args) {
+interface NewArgs {
+  _?: string[]
+  p?: string
+  path?: string
+  s?: string
+  slug?: string
+  r?: boolean
+  replace?: boolean
+  [key: string]: any
+}
+
+function newConsole(this: Hexo, args: NewArgs) {
   const path = args.p || args.path;
-  let title;
+  let title: string;
   if (args._.length) {
     title = args._.pop();
   } else if (path) {
@@ -30,7 +41,7 @@ function newConsole(this: Hexo, args) {
     title = basename(path);
   } else {
     // Display help message if user didn't input any arguments
-    return this.call('help', {_: ['new']});
+    return this.call('help', { _: ['new'] });
   }
 
   const data = {
diff --git a/lib/plugins/console/publish.ts b/lib/plugins/console/publish.ts
index 6f97f9d175..38913e8316 100644
--- a/lib/plugins/console/publish.ts
+++ b/lib/plugins/console/publish.ts
@@ -2,7 +2,14 @@ import tildify from 'tildify';
 import { magenta } from 'picocolors';
 import type Hexo from '../../hexo';
 
-function publishConsole(this: Hexo, args) {
+interface PublishArgs {
+  _: string[]
+  r?: boolean
+  replace?: boolean
+  [key: string]: any
+}
+
+function publishConsole(this: Hexo, args: PublishArgs) {
   // Display help message if user didn't input any arguments
   if (!args._.length) {
     return this.call('help', {_: ['publish']});
diff --git a/lib/plugins/console/render.ts b/lib/plugins/console/render.ts
index c40230f728..68cb95a710 100644
--- a/lib/plugins/console/render.ts
+++ b/lib/plugins/console/render.ts
@@ -5,7 +5,16 @@ import { writeFile } from 'hexo-fs';
 import { cyan, magenta } from 'picocolors';
 import type Hexo from '../../hexo';
 
-function renderConsole(this: Hexo, args) {
+interface RenderArgs {
+  _: string[]
+  o?: string
+  output?: string
+  pretty?: boolean
+  engine?: string
+  [key: string]: any
+}
+
+function renderConsole(this: Hexo, args: RenderArgs) {
   // Display help message if user didn't input any arguments
   if (!args._.length) {
     return this.call('help', {_: 'render'});
diff --git a/lib/plugins/filter/after_post_render/excerpt.ts b/lib/plugins/filter/after_post_render/excerpt.ts
index 5694ce5dec..bd7e49eda2 100644
--- a/lib/plugins/filter/after_post_render/excerpt.ts
+++ b/lib/plugins/filter/after_post_render/excerpt.ts
@@ -1,6 +1,8 @@
+import type { RenderData } from '../../../types';
+
 const rExcerpt = /<!-- ?more ?-->/i;
 
-function excerptFilter(data): void {
+function excerptFilter(data: RenderData): void {
   const { content } = data;
 
   if (typeof data.excerpt !== 'undefined') {
diff --git a/lib/plugins/filter/after_post_render/external_link.ts b/lib/plugins/filter/after_post_render/external_link.ts
index dab35b3a9d..8545ada191 100644
--- a/lib/plugins/filter/after_post_render/external_link.ts
+++ b/lib/plugins/filter/after_post_render/external_link.ts
@@ -1,12 +1,14 @@
 import { isExternalLink } from 'hexo-util';
 import type Hexo from '../../../hexo';
+import type { RenderData } from '../../../types';
+
 let EXTERNAL_LINK_POST_ENABLED = true;
 const rATag = /<a(?:\s+?|\s+?[^<>]+?\s+?)href=["']((?:https?:|\/\/)[^<>"']+)["'][^<>]*>/gi;
 const rTargetAttr = /target=/i;
 const rRelAttr = /rel=/i;
 const rRelStrAttr = /rel=["']([^<>"']*)["']/i;
 
-function externalLinkFilter(this: Hexo, data): void {
+function externalLinkFilter(this: Hexo, data: RenderData): void {
   if (!EXTERNAL_LINK_POST_ENABLED) return;
 
   const { external_link, url } = this.config;
diff --git a/lib/plugins/filter/before_exit/save_database.ts b/lib/plugins/filter/before_exit/save_database.ts
index 9a853eb93e..7c180edfd6 100644
--- a/lib/plugins/filter/before_exit/save_database.ts
+++ b/lib/plugins/filter/before_exit/save_database.ts
@@ -1,6 +1,6 @@
 import type Hexo from '../../../hexo';
 
-function saveDatabaseFilter(this: Hexo) {
+function saveDatabaseFilter(this: Hexo): Promise<void> {
   if (!this.env.init || !this._dbLoaded) return;
 
   return this.database.save().then(() => {
diff --git a/lib/plugins/filter/before_post_render/backtick_code_block.ts b/lib/plugins/filter/before_post_render/backtick_code_block.ts
index 7952169edd..8b40231875 100644
--- a/lib/plugins/filter/before_post_render/backtick_code_block.ts
+++ b/lib/plugins/filter/before_post_render/backtick_code_block.ts
@@ -1,10 +1,11 @@
 import type Hexo from '../../../hexo';
+import type { RenderData } from '../../../types';
 
 const rBacktick = /^((?:[^\S\r\n]*>){0,3}[^\S\r\n]*)(`{3,}|~{3,})[^\S\r\n]*((?:.*?[^`\s])?)[^\S\r\n]*\n((?:[\s\S]*?\n)?)(?:(?:[^\S\r\n]*>){0,3}[^\S\r\n]*)\2[^\S\r\n]?(\n+|$)/gm;
 const rAllOptions = /([^\s]+)\s+(.+?)\s+(https?:\/\/\S+|\/\S+)\s*(.+)?/;
 const rLangCaption = /([^\s]+)\s*(.+)?/;
 
-const escapeSwigTag = str => str.replace(/{/g, '&#123;').replace(/}/g, '&#125;');
+const escapeSwigTag = (str: string) => str.replace(/{/g, '&#123;').replace(/}/g, '&#125;');
 
 interface Options {
   lang: string,
@@ -13,8 +14,8 @@ interface Options {
   firstLineNumber?: string | number
 }
 
-export = (ctx: Hexo) => {
-  return function backtickCodeBlock(data): void {
+export = (ctx: Hexo): (data: RenderData) => void => {
+  return function backtickCodeBlock(data: RenderData): void {
     const dataContent = data.content;
 
     if ((!dataContent.includes('```') && !dataContent.includes('~~~')) || !ctx.extend.highlight.query(ctx.config.syntax_highlighter)) return;
@@ -27,7 +28,7 @@ export = (ctx: Hexo) => {
 
       // Extract language and caption of code blocks
       const args = _args.split('=').shift();
-      let lang, caption;
+      let lang: string, caption: string;
 
       if (args) {
         const match = rAllOptions.exec(args) || rLangCaption.exec(args);
diff --git a/lib/plugins/filter/before_post_render/titlecase.ts b/lib/plugins/filter/before_post_render/titlecase.ts
index bd149d3823..3362bda8a5 100644
--- a/lib/plugins/filter/before_post_render/titlecase.ts
+++ b/lib/plugins/filter/before_post_render/titlecase.ts
@@ -1,6 +1,8 @@
+import type { RenderData } from '../../../types';
+
 let titlecase;
 
-function titlecaseFilter(data): void {
+function titlecaseFilter(data: RenderData): void {
   if (!(typeof data.titlecase !== 'undefined' ? data.titlecase : this.config.titlecase) || !data.title) return;
 
   if (!titlecase) titlecase = require('titlecase');
diff --git a/lib/plugins/filter/new_post_path.ts b/lib/plugins/filter/new_post_path.ts
index 1eaa58c9f2..c204303fcf 100644
--- a/lib/plugins/filter/new_post_path.ts
+++ b/lib/plugins/filter/new_post_path.ts
@@ -4,7 +4,9 @@ import Promise from 'bluebird';
 import { createSha1Hash, Permalink } from 'hexo-util';
 import { ensurePath } from 'hexo-fs';
 import type Hexo from '../../hexo';
-let permalink;
+import type { PostSchema } from '../../types';
+
+let permalink: Permalink;
 
 const reservedKeys = {
   year: true,
@@ -16,14 +18,7 @@ const reservedKeys = {
   hash: true
 };
 
-interface Data {
-  path?: string;
-  layout?: string;
-  slug?: string;
-  date?: Date;
-}
-
-function newPostPathFilter(this: Hexo, data: Data = {}, replace): Promise<string> {
+function newPostPathFilter(this: Hexo, data: PostSchema = {}, replace: boolean): Promise<string> {
   const sourceDir = this.source_dir;
   const draftDir = join(sourceDir, '_drafts');
   const postDir = join(sourceDir, '_posts');
diff --git a/lib/plugins/filter/post_permalink.ts b/lib/plugins/filter/post_permalink.ts
index 5c92f7fc87..141408d391 100644
--- a/lib/plugins/filter/post_permalink.ts
+++ b/lib/plugins/filter/post_permalink.ts
@@ -1,9 +1,11 @@
 import { createSha1Hash, Permalink, slugize } from 'hexo-util';
 import { basename } from 'path';
 import type Hexo from '../../hexo';
-let permalink;
+import type { PostSchema } from '../../types';
 
-function postPermalinkFilter(this: Hexo, data) {
+let permalink: Permalink;
+
+function postPermalinkFilter(this: Hexo, data: PostSchema): string {
   const { config } = this;
   const { id, _id, slug, title, date } = data;
   let { __permalink } = data;
diff --git a/lib/plugins/filter/template_locals/i18n.ts b/lib/plugins/filter/template_locals/i18n.ts
index a709fe8934..87c505280b 100644
--- a/lib/plugins/filter/template_locals/i18n.ts
+++ b/lib/plugins/filter/template_locals/i18n.ts
@@ -1,7 +1,8 @@
 import { Pattern } from 'hexo-util';
 import type Hexo from '../../../hexo';
+import type { LocalsType } from '../../../types';
 
-function i18nLocalsFilter(this: Hexo, locals): void {
+function i18nLocalsFilter(this: Hexo, locals: LocalsType): void {
   const { i18n } = this.theme;
   const { config } = this;
   const i18nDir = config.i18n_dir;
diff --git a/lib/plugins/generator/asset.ts b/lib/plugins/generator/asset.ts
index 074f497620..336c4e2612 100644
--- a/lib/plugins/generator/asset.ts
+++ b/lib/plugins/generator/asset.ts
@@ -5,6 +5,7 @@ import { extname } from 'path';
 import { magenta } from 'picocolors';
 import type warehouse from 'warehouse';
 import type Hexo from '../../hexo';
+import type { AssetGenerator } from '../../types';
 
 interface Data {
   modified: boolean;
@@ -36,7 +37,7 @@ const process = (name: string, ctx: Hexo) => {
       data.data = () => ctx.render.render({
         path: source,
         toString: true
-      }).catch(err => {
+      }).catch((err: Error) => {
         ctx.log.error({err}, 'Asset render failed: %s', magenta(path));
       });
     } else {
@@ -47,7 +48,7 @@ const process = (name: string, ctx: Hexo) => {
   });
 };
 
-function assetGenerator(this: Hexo): Promise<any[]> {
+function assetGenerator(this: Hexo): Promise<AssetGenerator[]> {
   return Promise.all([
     process('Asset', this),
     process('PostAsset', this)
diff --git a/lib/plugins/generator/page.ts b/lib/plugins/generator/page.ts
index 8dbbcd817c..da2cf08c8b 100644
--- a/lib/plugins/generator/page.ts
+++ b/lib/plugins/generator/page.ts
@@ -1,5 +1,7 @@
-function pageGenerator(locals) {
-  return locals.pages.map(page => {
+import type { PageGenerator, PageSchema, SiteLocals } from '../../types';
+
+function pageGenerator(locals: SiteLocals): PageGenerator[] {
+  return locals.pages.map((page: PageSchema) => {
     const { path, layout } = page;
 
     if (!layout || layout === 'false' || layout === 'off') {
diff --git a/lib/plugins/generator/post.ts b/lib/plugins/generator/post.ts
index 4deec563dd..d97030b04f 100644
--- a/lib/plugins/generator/post.ts
+++ b/lib/plugins/generator/post.ts
@@ -1,8 +1,10 @@
-function postGenerator(locals) {
+import type { PostGenerator, PostSchema, SiteLocals } from '../../types';
+
+function postGenerator(locals: SiteLocals): PostGenerator[] {
   const posts = locals.posts.sort('-date').toArray();
   const { length } = posts;
 
-  return posts.map((post, i) => {
+  return posts.map((post: PostSchema, i: number) => {
     const { path, layout } = post;
 
     if (!layout || layout === 'false') {
diff --git a/lib/plugins/helper/date.ts b/lib/plugins/helper/date.ts
index 8d45b27147..063a437cb4 100644
--- a/lib/plugins/helper/date.ts
+++ b/lib/plugins/helper/date.ts
@@ -1,7 +1,7 @@
 import moment from 'moment-timezone';
 const { isMoment } = moment;
 import moize from 'moize';
-import type Hexo from '../../hexo';
+import type { LocalsType } from '../../types';
 
 const isDate = (value: moment.MomentInput | moment.Moment): boolean =>
   typeof value === 'object' && value instanceof Date && !isNaN(value.getTime());
@@ -61,7 +61,7 @@ function timeTagHelper(date: string | number | Date | moment.Moment, format: str
   return `<time datetime="${toISOString(date)}">${this.date(date, format, getLanguage(this), config.timezone)}</time>`;
 }
 
-function getLanguage(ctx) {
+function getLanguage(ctx: LocalsType) {
   return ctx.page.lang || ctx.page.language || ctx.config.language;
 }
 
diff --git a/lib/plugins/helper/is.ts b/lib/plugins/helper/is.ts
index 1f843cf3ff..ef9ec0fc46 100644
--- a/lib/plugins/helper/is.ts
+++ b/lib/plugins/helper/is.ts
@@ -1,4 +1,4 @@
-function isCurrentHelper(path = '/', strict) {
+function isCurrentHelper(path = '/', strict: boolean) {
   const currentPath = this.path.replace(/^[^/].*/, '/$&');
 
   if (strict) {
diff --git a/lib/plugins/highlight/highlight.ts b/lib/plugins/highlight/highlight.ts
index 787017fcf7..04d507ec92 100644
--- a/lib/plugins/highlight/highlight.ts
+++ b/lib/plugins/highlight/highlight.ts
@@ -1,8 +1,22 @@
+import type Hexo from '../../hexo';
+
+interface Options {
+  line_threshold?: number;
+  line_number?: boolean;
+  lines_length?: number;
+  language_attr?: boolean;
+  caption?: string;
+  firstLine?: number;
+  lang?: string;
+  mark?: number[];
+  firstLineNumber?: number;
+}
+
 // Lazy require highlight.js
 let highlight;
 
-module.exports = function highlightFilter(code, options) {
-  const hljsCfg = this.config.highlight || {};
+module.exports = function highlightFilter(this: Hexo, code: string, options: Options) {
+  const hljsCfg = this.config.highlight || {} as any;
   const line_threshold = options.line_threshold || hljsCfg.line_threshold || 0;
   const shouldUseLineNumbers = typeof options.line_number === 'undefined' ? hljsCfg.line_number : options.line_number;
   const surpassesLineThreshold = options.lines_length > line_threshold;
diff --git a/lib/plugins/injector/index.ts b/lib/plugins/injector/index.ts
index 6736417bc8..4c640279c1 100644
--- a/lib/plugins/injector/index.ts
+++ b/lib/plugins/injector/index.ts
@@ -1,6 +1,6 @@
 import type Hexo from '../../hexo';
 
 export = (ctx: Hexo) => {
-  // eslint-disable-next-line no-unused-vars
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
   const { injector } = ctx.extend;
 };
diff --git a/lib/plugins/renderer/json.ts b/lib/plugins/renderer/json.ts
index c5d02377f9..e4833402c3 100644
--- a/lib/plugins/renderer/json.ts
+++ b/lib/plugins/renderer/json.ts
@@ -1,6 +1,6 @@
 import type { StoreFunctionData } from '../../extend/renderer';
 
-function jsonRenderer(data: StoreFunctionData) {
+function jsonRenderer(data: StoreFunctionData): any {
   return JSON.parse(data.text);
 }
 
diff --git a/lib/plugins/renderer/nunjucks.ts b/lib/plugins/renderer/nunjucks.ts
index ccb0281346..1b854f1ebc 100644
--- a/lib/plugins/renderer/nunjucks.ts
+++ b/lib/plugins/renderer/nunjucks.ts
@@ -22,7 +22,7 @@ function toArray(value) {
   return [];
 }
 
-function safeJsonStringify(json, spacer = undefined) {
+function safeJsonStringify(json: any, spacer = undefined): string {
   if (typeof json !== 'undefined' && json !== null) {
     return JSON.stringify(json, null, spacer);
   }
@@ -37,12 +37,12 @@ const nunjucksCfg = {
   lstripBlocks: false
 };
 
-const nunjucksAddFilter = (env: Environment) => {
+const nunjucksAddFilter = (env: Environment): void => {
   env.addFilter('toarray', toArray);
   env.addFilter('safedump', safeJsonStringify);
 };
 
-function njkCompile(data: StoreFunctionData) {
+function njkCompile(data: StoreFunctionData): nunjucks.Template {
   let env: Environment;
   if (data.path) {
     env = nunjucks.configure(dirname(data.path), nunjucksCfg);
@@ -56,11 +56,11 @@ function njkCompile(data: StoreFunctionData) {
   return nunjucks.compile(text as string, env, data.path);
 }
 
-function njkRenderer(data: StoreFunctionData, locals: object) {
+function njkRenderer(data: StoreFunctionData, locals: object): string {
   return njkCompile(data).render(locals);
 }
 
-njkRenderer.compile = (data: StoreFunctionData) => {
+njkRenderer.compile = (data: StoreFunctionData): (locals: any) => string => {
   // Need a closure to keep the compiled template.
   return locals => njkCompile(data).render(locals);
 };
diff --git a/lib/plugins/renderer/plain.ts b/lib/plugins/renderer/plain.ts
index 99c35a1c1c..f537106a8d 100644
--- a/lib/plugins/renderer/plain.ts
+++ b/lib/plugins/renderer/plain.ts
@@ -1,6 +1,6 @@
 import type { StoreFunctionData } from '../../extend/renderer';
 
-function plainRenderer(data: StoreFunctionData) {
+function plainRenderer(data: StoreFunctionData): string {
   return data.text;
 }
 
diff --git a/lib/plugins/renderer/yaml.ts b/lib/plugins/renderer/yaml.ts
index fd460d14a0..ceef7f7a15 100644
--- a/lib/plugins/renderer/yaml.ts
+++ b/lib/plugins/renderer/yaml.ts
@@ -3,7 +3,7 @@ import { escape } from 'hexo-front-matter';
 import logger from 'hexo-log';
 import type { StoreFunctionData } from '../../extend/renderer';
 
-let schema = {};
+let schema: yaml.Schema;
 // FIXME: workaround for https://github.com/hexojs/hexo/issues/4917
 try {
   schema = yaml.DEFAULT_SCHEMA.extend(require('js-yaml-js-types').all);
@@ -15,7 +15,7 @@ try {
   }
 }
 
-function yamlHelper(data: StoreFunctionData) {
+function yamlHelper(data: StoreFunctionData): any {
   return yaml.load(escape(data.text), { schema });
 }
 
diff --git a/lib/theme/index.ts b/lib/theme/index.ts
index aff5a74711..41c83d6bfe 100644
--- a/lib/theme/index.ts
+++ b/lib/theme/index.ts
@@ -7,15 +7,19 @@ import { i18n } from './processors/i18n';
 import { source } from './processors/source';
 import { view } from './processors/view';
 import type Hexo from '../hexo';
+import type { Pattern } from 'hexo-util';
 
 class Theme extends Box {
-  public config: any;
-  public views: any;
+  public config: object;
+  public views: Record<string, Record<string, View>>;
   public i18n: I18n;
-  public View: any;
-  public processors: any[];
+  public View: typeof View;
+  public processors: {
+    pattern: Pattern;
+    process: (...args: any[]) => any;
+  }[];
 
-  constructor(ctx: Hexo, options?) {
+  constructor(ctx: Hexo, options?: object) {
     super(ctx, ctx.theme_dir, options);
 
     this.config = {};
@@ -48,7 +52,7 @@ class Theme extends Box {
     _View.prototype._helper = ctx.extend.helper;
   }
 
-  getView(path: string) {
+  getView(path: string): View {
     // Replace backslashes on Windows
     path = path.replace(/\\/g, '/');
 
@@ -65,7 +69,7 @@ class Theme extends Box {
     return views[Object.keys(views)[0]];
   }
 
-  setView(path: string, data) {
+  setView(path: string, data: string): void {
     const ext = extname(path);
     const name = path.substring(0, path.length - ext.length);
     this.views[name] = this.views[name] || {};
@@ -74,7 +78,7 @@ class Theme extends Box {
     views[ext] = new this.View(path, data);
   }
 
-  removeView(path: string) {
+  removeView(path: string): void {
     const ext = extname(path);
     const name = path.substring(0, path.length - ext.length);
     const views = this.views[name];
diff --git a/lib/theme/processors/view.ts b/lib/theme/processors/view.ts
index c127d02e7c..89d5205423 100644
--- a/lib/theme/processors/view.ts
+++ b/lib/theme/processors/view.ts
@@ -2,7 +2,7 @@ import { Pattern } from 'hexo-util';
 import type { _File } from '../../box';
 import type Theme from '..';
 
-function process(file: _File) {
+function process(file: _File): Promise<void> {
   const { path } = file.params;
 
   if (file.type === 'delete') {
diff --git a/lib/theme/view.ts b/lib/theme/view.ts
index af4c75be62..c693a3ded5 100644
--- a/lib/theme/view.ts
+++ b/lib/theme/view.ts
@@ -3,6 +3,8 @@ import { parse as yfm } from 'hexo-front-matter';
 import Promise from 'bluebird';
 import type Theme from '.';
 import type Render from '../hexo/render';
+import type { NodeJSLikeCallback } from '../types';
+import type { Helper } from '../extend';
 
 const assignIn = (target: any, ...sources: any[]) => {
   const length = sources.length;
@@ -24,15 +26,15 @@ class Options {
 
 class View {
   public path: string;
-  public source: any;
+  public source: string;
   public _theme: Theme;
   public data: any;
   public _compiled: any;
   public _compiledSync: any;
-  public _helper: any;
+  public _helper: Helper;
   public _render: Render;
 
-  constructor(path: string, data) {
+  constructor(path: string, data: string) {
     this.path = path;
     this.source = join(this._theme.base, 'layout', path);
     this.data = typeof data === 'string' ? yfm(data) : data;
@@ -40,16 +42,16 @@ class View {
     this._precompile();
   }
 
-  // eslint-disable-next-line @typescript-eslint/ban-types
-  render(options: Options | Function = {}, callback) {
+  render(callback: NodeJSLikeCallback<any>): Promise<any>;
+  render(options: Options, callback?: NodeJSLikeCallback<any>): Promise<any>;
+  render(options: Options | NodeJSLikeCallback<any> = {}, callback?: NodeJSLikeCallback<any>): Promise<any> {
     if (!callback && typeof options === 'function') {
       callback = options;
       options = {};
     }
     const { data } = this;
-    // eslint-disable-next-line no-extra-parens
     const { layout = (options as Options).layout } = data;
-    const locals = this._buildLocals(options);
+    const locals = this._buildLocals(options as Options);
 
     return this._compiled(this._bindHelpers(locals)).then(result => {
       if (result == null || !layout) return result;
@@ -87,8 +89,8 @@ class View {
     return layoutView.renderSync(layoutLocals);
   }
 
-  _buildLocals(locals) {
-    // eslint-disable-next-line no-unused-vars
+  _buildLocals(locals: Options) {
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
     const { layout, _content, ...data } = this.data;
     return assignIn({}, locals, data, {
       filename: this.source
@@ -106,7 +108,7 @@ class View {
     return locals;
   }
 
-  _resolveLayout(name: string) {
+  _resolveLayout(name: string): View {
     // Relative path
     const layoutPath = join(dirname(this.path), name);
     let layoutView = this._theme.getView(layoutPath);
@@ -118,7 +120,7 @@ class View {
     if (layoutView && layoutView.source !== this.source) return layoutView;
   }
 
-  _precompile() {
+  _precompile(): void {
     const render = this._render;
     const ctx = render.context;
     const ext = extname(this.path);
diff --git a/lib/types.ts b/lib/types.ts
index ea6313c253..6959a456cc 100644
--- a/lib/types.ts
+++ b/lib/types.ts
@@ -1 +1,129 @@
-type NodeJSLikeCallback<R, E = any> = (err: E, result?: R) => void
+import moment from 'moment';
+import type default_config from './hexo/default_config';
+
+export type NodeJSLikeCallback<R, E = any> = (err: E, result?: R) => void
+
+export interface RenderData {
+  engine?: string;
+  content?: string;
+  disableNunjucks?: boolean;
+  markdown?: object;
+  source?: string;
+  titlecase?: boolean;
+  title?: string;
+  excerpt?: string;
+  more?: string;
+}
+
+// Schema
+export interface PostSchema {
+  id?: string;
+  _id?: string;
+  title?: string;
+  date?: moment.Moment,
+  updated?: moment.Moment,
+  comments?: boolean;
+  layout?: string;
+  _content?: string;
+  source?: string;
+  slug?: string;
+  photos?: string[];
+  raw?: string;
+  published?: boolean;
+  content?: string;
+  excerpt?: string;
+  more?: string;
+  author?: string;
+  asset_dir?: string;
+  full_source?: string;
+  path?: string;
+  permalink?: string;
+  categories?: any;
+  tags?: any;
+  __permalink?: string;
+  __post?: boolean;
+  canonical_path?: string;
+  lang?: string;
+  language?: string;
+  prev?: PostSchema;
+  next?: PostSchema;
+}
+
+export interface PageSchema {
+  _id?: string;
+  title?: string;
+  date?: moment.Moment,
+  updated?: moment.Moment,
+  comments?: boolean;
+  layout?: string;
+  _content?: string;
+  source?: string;
+  path?: string;
+  raw?: string;
+  content?: string;
+  excerpt?: string;
+  more?: string;
+  author?: string;
+  full_source?: string;
+  permalink?: string;
+  tags?: any;
+  canonical_path?: string;
+  lang?: string;
+  language?: string;
+  __page?: boolean;
+}
+
+export interface LocalsType {
+  page: PostSchema | PageSchema;
+  path: string;
+  url: string;
+  config: typeof default_config;
+  theme: object;
+  layout: string;
+  env: any;
+  view_dir: string;
+  site: object;
+  cache?: boolean;
+  __?: (key: string) => string;
+  _p?: (key: string, options?: any) => string;
+}
+
+// Generator return types
+export interface AssetGenerator {
+  path: string;
+  data: {
+    modified: boolean;
+    data?: () => any;
+  }
+}
+
+export type SimplePostGenerator = {
+  path: string;
+  data: string;
+}
+export type NormalPostGenerator = {
+  path: string;
+  layout: string[];
+  data: PostSchema;
+}
+export type PostGenerator = SimplePostGenerator | NormalPostGenerator;
+
+
+export type SimplePageGenerator = {
+  path: string;
+  data: string;
+}
+export type NormalPageGenerator = {
+  path: string;
+  layout: string[];
+  data: PageSchema;
+}
+export type PageGenerator = SimplePageGenerator | NormalPageGenerator;
+
+export interface SiteLocals {
+  posts: any; // _Query
+  pages: any; // _Query
+  categories: any; // _Model
+  tags: any; // _Model
+  data: object;
+}
diff --git a/package.json b/package.json
index 59b2569d53..6322eb4d52 100644
--- a/package.json
+++ b/package.json
@@ -66,7 +66,9 @@
     "warehouse": "^5.0.0"
   },
   "devDependencies": {
+    "@types/abbrev": "^1.1.3",
     "@types/bluebird": "^3.5.37",
+    "@types/js-yaml": "^4.0.9",
     "@types/node": "^18.11.8",
     "@types/nunjucks": "^3.2.2",
     "@types/text-table": "^0.2.4",