With the Nu Html Checker (vnu), you can:

• catch unintended mistakes in your HTML, CSS, and SVG
• batch-check documents from the command line and from other scripts/apps
• deploy your own instance of the vnu checker as a service (like validator.w3.org/nu)

You can run the vnu checker with one of the invocations from the vnu manual page. For example:

java -jar ~/vnu.jar [OPTIONS]... FILES|DIRECTORY|URL...

The OPTIONS section of the vnu manual page has details on all available options.

The vnu source code is available on GitHub, as are instructions on how to build, test, and run the code.

The Nu Html Checker (vnu) is released upstream in these formats:

• pre-compiled Linux, Windows, and macOS binaries that include an embedded Java runtime
• vnu.jar — a portable version you can use on any system that has Java 11 or above installed
• vnu.war — for deploying the vnu checker service through a servlet container such as Tomcat

A Dockerfile (see Pulling the Docker image below) and npm, pip, and brew packages are also available.

You can get the latest release or run one of the following:

• docker run -it --rm -p 8888:8888 ghcr.io/validator/validator:latest
• npm install vnu-jar
• npm install --registry=https://npm.pkg.github.com @validator/vnu-jar
• brew install vnu
• pip install html5validator

…and see the Usage and Web-based checking sections here. Or automate your checking with a frontend such as:

• Grunt plugin for HTML validation or Gulp plugin for HTML validation or Maven plugin for HTML validation
• html5validator pip package (for integration in Travis CI, CircleCI, CodeShip, Jekyll, Pelican, etc.)
• LMVTFY: Let Me Validate That For You (auto-check JSFiddle/JSBin, etc., links in GitHub issue comments)

The Nu Html Checker (vnu) — along with being usable as a standalone command-line client — can be run as an HTTP service, similar to validator.w3.org/nu, for browser-based checking of HTML documents, CSS stylesheets, and SVG images over the Web. To that end, the vnu checker is released as several separate packages:

• Linux, Windows, and macOS binaries for deploying a self-contained service on any system
• vnu.jar for deploying a self-contained service on a system with Java installed
• vnu.war for deploying to a servlet container such as Tomcat

All deployments expose a REST API that enables checking of HTML documents, CSS stylesheets, and SVG images from other clients, not just web browsers. And the Linux, Windows, and macOS binaries and vnu.jar package also include a simple HTTP client that enables you to either send documents to a locally-running instance of the vnu checker HTTP service — for fast command-line checking — or to any remote instance of the vnu checker HTTP service running anywhere on the Web.

The latest releases of the Linux, Windows, and macOS binaries and vnu.jar and vnu.war packages are available from the validator project at github. The following are detailed instructions on using them.

See vnu-server for invocation manual page.

To run the vnu checker inside of an existing servlet container such as Apache Tomcat you will need to deploy the vnu.war file to that server following its documentation. For example, on Apache Tomcat you could do this using the Manager application or simply by copying the file to the webapps directory (since that is the default appBase setting). Typically you would see a message similar to the following in the catalina.out log file.

May 7, 2014 4:42:04 PM org.apache.catalina.startup.HostConfig deployWAR
INFO: Deploying web application archive /var/lib/tomcat7/webapps/vnu.war

Assuming your servlet container is configured to receive HTTP requests sent to localhost on port 80 and the context root of this application is vnu (often the default behavior is to use the WAR file's filename as the context root unless one is explicitly specified) you should be able to access the application by connecting to http://localhost/vnu/.

<!--
  <filter>
      <filter-name>inbound-size-limit-filter</filter-name>
      <filter-class>nu.validator.servlet.InboundSizeLimitFilter</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>inbound-size-limit-filter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
-->

The vnu checker is packaged with an HTTP client you can use from the command line to either send documents to a locally-running instance of the vnu checker HTTP service — for fast command-line checking — or to a remote instance anywhere on the Web.

To check documents locally using the packaged HTTP client, do this:

1. Start up the vnu checker as a local HTTP service, as described in the Standalone web server section.

2. Invoke the HTTP client like from the commandline according to vnu-client manual page.

You can pull the vnu Docker image from https://ghcr.io/validator/validator in the GitHub container registry.

To pull and run the latest version of the vnu checker:

  docker run -it --rm -p 8888:8888 ghcr.io/validator/validator:latest

To pull and run a specific tag/version of the vnu checker from the container registry — for example, the 17.11.1 version:

  docker run -it --rm -p 8888:8888 ghcr.io/validator/validator:17.11.1

To bind the vnu checker to a specific address (rather than have it listening on all interfaces):

  docker run -it --rm -p 128.30.52.73:8888:8888 ghcr.io/validator/validator:latest

To make the vnu checker run with a connection timeout and socket timeout different from the default 5 seconds, use the CONNECTION_TIMEOUT_SECONDS and SOCKET_TIMEOUT_SECONDS environment variables:

  docker run -it --rm \
     -e CONNECTION_TIMEOUT_SECONDS=15 \
     -e SOCKET_TIMEOUT_SECONDS=15 \
     -p 8888:8888 \
     validator/validator

To make the vnu checker run with particular Java system properties set, use the JAVA_TOOL_OPTIONS environment variable:

  docker run -it --rm \
     -e JAVA_TOOL_OPTIONS=-Dnu.validator.client.asciiquotes=yes  \
     -p 8888:8888 \
     validator/validator

To define a service named vnu for use with docker compose, create a Compose file named docker-compose.yml (for example), with contents such as the following:

  version: '2' services:
    vnu:
      image: validator/validator ports:
        - "8888:8888"
      network_mode: "host" #so "localhost" refers to the host machine.

Follow the steps below to build, test, and run the vnu checker such that you can open http://0.0.0.0:8888/ in a Web browser to use the vnu checker Web UI.

1. Make sure you have git, python, JDK 8 or above and ant installed.

2. Set the JAVA_HOME environment variable:

   export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64    <-- Ubuntu, etc.
   
   export JAVA_HOME=$(/usr/libexec/java_home)            <-- macOS
   

3. Create a working directory:

   git clone https://github.com/validator/validator.git
   

4. Change into your working directory:

   cd validator
   

5. Start the checker.py Python script:

   python ./checker.py all
   

The first time you run the checker.py Python script, you’ll need to be online and the build will need time to download several megabytes of dependencies.

Alternatively, if you wish to first download all dependencies, and build later when offline:

1. Use the dldeps task to download

    python ./checker.py dldeps
   

2. For all operations when offline, use the --offline option (place it before the task name)

    python ./checker.py --offline all
   

The steps above will build, test, and run the vnu checker such that you can open http://0.0.0.0:8888/ in a Web browser to use the vnu checker Web UI.

python ./checker.py --bind-address=128.30.52.73 all

Use python ./checker.py --help to see command-line options for controlling the behavior of the script, as well as build-target names you can call separately; e.g.:

python ./checker.py build       # to build only

python ./checker.py build test  # to build and test

python ./checker.py run         # to run only

python ./checker.py jar         # to compile vnu.jar

python ./checker.py update-shallow && \
  python ./checker.py dldeps && \
  python ./checker.py jar       # to compile vnu.jar faster

Additional documentation is available on the vnu wiki.