diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 312d20a..b6a9619 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -57,10 +57,11 @@ jobs:
           wasm32-wasi-cabal build pandoc-cli
           popd
 
-      - name: wasm-opt
+      - name: dist
         run: |
           mkdir dist
           wasm-opt --low-memory-unused --converge --gufa --flatten --rereloop -Oz $(find pandoc -type f -name pandoc.wasm) -o dist/pandoc.wasm
+          cp frontend/*.html frontend/*.js dist
 
       - name: test
         run: |
diff --git a/frontend/index.html b/frontend/index.html
new file mode 100644
index 0000000..d47461d
--- /dev/null
+++ b/frontend/index.html
@@ -0,0 +1,92 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>pandoc-wasm playground</title>
+    <style>
+      body {
+        display: flex;
+        flex-direction: column;
+        height: 100vh;
+        margin: 0;
+        font-family: monospace;
+      }
+
+      #container {
+        display: flex;
+        flex: 1;
+        overflow: hidden;
+      }
+
+      textarea {
+        width: 50%;
+        height: 100%;
+        border: none;
+        padding: 1rem;
+        resize: none;
+        box-sizing: border-box;
+        font-size: 1rem;
+        font-family: monospace;
+      }
+
+      #input {
+        border-right: 1px solid #ccc;
+      }
+
+      #output {
+        background-color: #f5f5f5;
+        color: #333;
+      }
+
+      #arguments-container {
+        padding: 0.5rem;
+        border-top: 1px solid #ccc;
+        background-color: #f9f9f9;
+      }
+
+      #arguments {
+        width: calc(100% - 1rem);
+        padding: 0.5rem;
+        font-size: 1rem;
+        box-sizing: border-box;
+        font-family: monospace;
+      }
+    </style>
+  </head>
+  <body>
+    <div id="container">
+      <textarea id="input" placeholder="Enter your input here..."></textarea>
+      <textarea
+        id="output"
+        readonly
+        placeholder="Output will be displayed here..."
+      ></textarea>
+    </div>
+    <div id="arguments-container">
+      <input type="text" id="arguments" value="-f markdown -t rst" />
+    </div>
+    <script type="module">
+      import { run_pandoc } from "./index.js";
+
+      async function updateOutput() {
+        const inputText = document.getElementById("input").value;
+        const argumentsText = document
+          .getElementById("arguments")
+          .value.trim()
+          .split(" ");
+        try {
+          const output = await run_pandoc(argumentsText, inputText);
+          document.getElementById("output").value = output;
+        } catch (err) {
+          document.getElementById("output").value = `Error: ${err.message}`;
+        }
+      }
+
+      document.getElementById("input").addEventListener("input", updateOutput);
+      document
+        .getElementById("arguments")
+        .addEventListener("input", updateOutput);
+    </script>
+  </body>
+</html>
diff --git a/frontend/index.js b/frontend/index.js
new file mode 100644
index 0000000..4d7928a
--- /dev/null
+++ b/frontend/index.js
@@ -0,0 +1,62 @@
+import {
+  WASI,
+  OpenFile,
+  File,
+  ConsoleStdout,
+} from "https://cdn.jsdelivr.net/npm/@bjorn3/browser_wasi_shim@0.3.0/dist/index.js";
+
+const mod = await WebAssembly.compileStreaming(fetch("./pandoc.wasm"));
+
+const instance_promise_pool_size = 8;
+
+const instance_promise_pool = [];
+
+function instance_promise_pool_fill() {
+  if (instance_promise_pool.length < instance_promise_pool_size) {
+    for (
+      let i = instance_promise_pool.length;
+      i < instance_promise_pool_size;
+      ++i
+    ) {
+      const args = [];
+      const env = [];
+      const stdin_file = new File(new Uint8Array(), { readonly: true });
+      const stdout_file = new File(new Uint8Array(), { readonly: false });
+      const fds = [
+        new OpenFile(stdin_file),
+        new OpenFile(stdout_file),
+        ConsoleStdout.lineBuffered((msg) =>
+          console.warn(`[WASI stderr] ${msg}`)
+        ),
+      ];
+      const options = { debug: false };
+      const wasi = new WASI(args, env, fds, options);
+      instance_promise_pool.push(
+        WebAssembly.instantiate(mod, {
+          wasi_snapshot_preview1: wasi.wasiImport,
+        }).then((instance) => ({ instance, wasi, stdin_file, stdout_file }))
+      );
+    }
+  }
+}
+
+instance_promise_pool_fill();
+
+const instances = (async function* () {
+  while (true) {
+    yield await instance_promise_pool.shift();
+    instance_promise_pool_fill();
+  }
+})();
+
+export async function run_pandoc(args, stdin_str) {
+  const { instance, wasi, stdin_file, stdout_file } = (await instances.next())
+    .value;
+  wasi.args = ["pandoc.wasm", ...args];
+  stdin_file.data = new TextEncoder().encode(stdin_str);
+  const ec = wasi.start(instance);
+  if (ec !== 0) {
+    throw new Error(`Non-zero exit code ${ec}`);
+  }
+  return new TextDecoder("utf-8", { fatal: true }).decode(stdout_file.data);
+}
