The Nu Html Checker (v.Nu) helps you catch unintended mistakes in your HTML, CSS, and SVG. It enables you to batch-check documents from the command line and from other scripts/apps, and to deploy your own instance of the checker as a service (like validator.w3.org/nu). Its source code is available, as are instructions on how to build, test, and run the code.

vnu.jar is a packaged version of the Nu Html Checker for batch-checking documents from the command line and from other scripts/apps.

You can work with vnu.jar in CommonJS modules.

npm install --save vnu-jar

npm install --save vnu-jar@next

'use strict';

const { execFile } = require('child_process');
const vnu = require('vnu-jar');

// Print path to vnu.jar
console.log(vnu);

// Work with vnu.jar, for example get vnu.jar version
execFile('java', ['-jar', `"${vnu}"`, '--version'], { shell: true }, (error, stdout) => {
    if (error) {
        console.error(`exec error: ${error}`);
        return;
    }

    console.log(stdout);
});

• vnu-runtime-image/bin/vnu OPTIONS FILES (Linux or macOS)

• vnu-runtime-image\bin\vnu.bat OPTIONS FILES (Windows)

• java -jar ~/vnu.jar OPTIONS FILES (any system with Java8+ installed)

…where FILES are the documents to check, and OPTIONS are zero or more of the following options:

--errors-only --Werror --exit-zero-always --stdout --asciiquotes
--user-agent USER_AGENT --no-langdetect --no-stream --filterfile FILENAME
--filterpattern PATTERN --css --skip-non-css --also-check-css --svg
--skip-non-svg --also-check-svg --xml --html --skip-non-html
--format gnu|xml|json|text --help --verbose --version

The Options section below provides details on each option, and the rest of this section provides some specific examples.

Note: Throughout these examples, replace ~/vnu.jar with the actual path to that jar file on your system, and replace vnu-runtime-image/bin/vnu and vnu-runtime-image\bin\vnu.bat with the actual path to the vnu or vnu.bat program on your system — or if you add the vnu-runtime-image/bin or vnu-runtime-image\bin directory your system PATH environment variable, you can invoke the checker with just vnu.

To check one or more documents from the command line:

  vnu-runtime-image/bin/vnu      FILE.html FILE2.html FILE3.html...

  vnu-runtime-image\bin\vnu.bat  FILE.html FILE2.html FILE3.html...

  java -jar ~/vnu.jar            FILE.html FILE2.html FILE3.html...

Note: If you get a StackOverflowError error when invoking the checker, try adjusting the thread stack size by providing the -Xss option to java:

  java -Xss512k -jar ~/vnu.jar ...

  vnu-runtime-image/bin/java -Xss512k \
      -m vnu/nu.validator.client.SimpleCommandLineValidator ...

To check all documents in a particular directory DIRECTORY_PATH as HTML:

  java -jar ~/vnu.jar            DIRECTORY_PATH

  vnu-runtime-image/bin/vnu      DIRECTORY_PATH

  vnu-runtime-image\bin\vnu.bat  DIRECTORY_PATH

Note: The examples in this section assume you have the vnu-runtime-image/bin or vnu-runtime-image\bin directory in your system PATH environment variable. If you’re using the jar file instead, replace vnu in the examples with java -jar ~/vnu.jar.

To check all documents in a particular directory DIRECTORY_PATH as HTML, but skip any documents whose names don’t end with the extensions .html, .htm, .xhtml, or .xht:

  vnu --skip-non-html DIRECTORY_PATH

To check all documents in a particular directory as CSS:

  vnu --css DIRECTORY_PATH

To check all documents in a particular directory as CSS, but skip any documents whose names don’t end with the extension .css:

  vnu --skip-non-css DIRECTORY_PATH

To check all documents in a particular directory, with documents whose names end in the extension .css being checked as CSS, and all other documents being checked as HTML:

  vnu --also-check-css DIRECTORY_PATH

To check all documents in a particular directory as SVG:

  vnu --svg DIRECTORY_PATH

To check all documents in a particular directory as SVG, but skip any documents whose names don’t end with the extension .svg:

  vnu --skip-non-svg DIRECTORY_PATH

To check all documents in a particular directory, with documents whose names end in the extension .svg being checked as SVG, and all other documents being checked as HTML:

  vnu --also-check-svg DIRECTORY_PATH

To check a Web document:

  vnu _URL_

  example: vnu http://example.com/foo

To check standard input:

  vnu -

  example:

  echo '<!doctype html><title>...' | vnu -

  echo '<!doctype html><title>...' | java -jar ~/vnu.jar -

When used from the command line as described in this section, the checker provides the following options:

Specifies whether ASCII quotation marks are substituted for Unicode smart
quotation marks in messages.

default: [unset; Unicode smart quotation marks are used in messages]

Specifies that only error-level messages and non-document-error messages are
reported (so that warnings and info messages are not reported).

default: [unset; all messages reported, including warnings & info messages]

Makes the checker exit non-zero if any warnings are encountered (even if
there are no errors).

default: [unset; checker exits zero if only warnings are encountered]

Makes the checker exit zero even if errors are reported for any documents.

default: [unset; checker exits 1 if errors are reported for any documents]

Makes the checker report errors and warnings to stdout rather than stderr.

default: [unset; checker reports errors and warnings to stderr]

Specifies a filename. Each line of the file contains either a regular
expression or starts with "#" to indicate the line is a comment. Any error
message or warning message that matches a regular expression in the file is
filtered out (dropped/suppressed).

default: [unset; checker does no message filtering]

Specifies a regular expression. Any error message or warning message that
matches the regular expression is filtered out (dropped/suppressed).

As with all other checker options, this option may only be specified once.
So to filter multiple error messages or warning messages, you must provide a
single regular expression that will match all the messages. The typical way
to do that for regular expressions is to OR multiple patterns together using
the "|" character.

default: [unset; checker does no message filtering]

Specifies the output format for reporting the results.

default: "gnu"

possible values: "gnu", "xml", "json", "text" [see information at URL below]

https://github.com/validator/validator/wiki/Service-%C2%BB-Common-params#out

Shows detailed usage information.

Check documents as CSS but skip documents that don’t have *.css extensions.

default: [unset; all documents found are checked]

Force all documents to be checked as CSS, regardless of extension.

default: [unset]

Check documents as SVG but skip documents that don’t have *.svg extensions.

default: [unset; all documents found are checked]

Force all documents to be checked as SVG, regardless of extension.

default: [unset]

Skip documents that don’t have *.html, *.htm, *.xhtml, or *.xht extensions.

default: [unset; all documents found are checked, regardless of extension]

Forces any *.xhtml or *.xht documents to be parsed using the HTML parser.

default: [unset; XML parser is used for *.xhtml and *.xht documents]

Forces any *.html documents to be parsed using the XML parser.

default: [unset; HTML parser is used for *.html documents]

Check CSS documents (in addition to checking HTML documents).

default: [unset; no documents are checked as CSS]

Check SVG documents (in addition to checking HTML documents).

default: [unset; no documents are checked as SVG]

Specifies the value of the User-Agent request header to send when checking
HTTPS/HTTP URLs.

default: "Validator.nu/LV"

Disables language detection, so that documents are not checked for missing
or mislabeled html[lang] attributes.

default: [unset; language detection & html[lang] checking are performed]

Forces all documents to be be parsed in buffered mode instead of streaming
mode (causes some parse errors to be treated as non-fatal document errors
instead of as fatal document errors).

default: [unset; non-streamable parse errors cause fatal document errors]

Specifies "verbose" output. (Currently this just means that the names of
files being checked are written to stdout.)

default: [unset; output is not verbose]

Shows the checker version number.