The Nu Html Checker (v.Nu) is the backend of checker.html5.org, html5.validator.nu, and validator.w3.org/nu. Its source code is available, as are instructions on how to build, test, and run the code. A Dockerfile (see the Pulling from Docker Hub section below) and npm, pip, and brew packages of it are also available, and it’s released upstream in these formats:
-
vnu.jaris a portable standalone version for batch-checking documents from the command line and from other scripts/apps, or for deploying the checker as a self-contained service -
vnu.waris for deploying the checker service through a servlet container such as Tomcat
Note: The vnu.jar and vnu.war files require an environment with Java 8 or above; they won’t run in Java 7 or older environment.
You can get the latest release or run docker run -it --rm -p 8888:8888 validator/validator:latest, npm install vnu-jar,
brew install vnu, or pip install html5validator and see the
Usage and Web-based checking sections below. Or automate your document
checking with a frontend such as:
-
Grunt plugin for HTML validation or Gulp plugin for HTML validation
-
html5validator
pippackage (for HTML checking integration in Travis CI, CircleCI, CodeShip, Jekyll, Pelican etc.) -
LMVTFY: Let Me Validate That For You (auto-check HTML of JSFiddle/JSBin etc. links in github issue comments)
Use the vnu.jar checker as an executable for command-line checking of
documents by invoking it like this:
java -jar ~/vnu.jar [--errors-only] [--Werror] [--exit-zero-always]
[--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] [--html] [--skip-non-html] [--format
gnu|xml|json|text] [--help] [--verbose] [--version] FILES
Note: In these instructions, replace "~/vnu.jar" with the actual path to the file on your system.
To check one or more documents from the command line:
java -jar ~/vnu.jar FILE.html FILE2.html FILE3.HTML FILE4.html...
Note: If you get a StackOverflowError error when using the vnu.jar file,
try adjusting the thread stack size by providing the -Xss option to java:
java -Xss512k -jar ~/vnu.jar FILE.html...
To check all documents in a particular directory as HTML:
java -jar ~/vnu.jar some-directory-name/
To check all documents in a particular directory as HTML, but skip any documents
whose names don’t end with the extensions .html, .htm, .xhtml, or .xht:
java -jar ~/vnu.jar --skip-non-html some-directory-name/
To check all documents in a particular directory as CSS:
java -jar ~/vnu.jar --force-css some-directory-name/
To check all documents in a particular directory as CSS, but skip any documents
whose names don’t end with the extension .css:
java -jar ~/vnu.jar --skip-non-css some-directory-name/
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:
java -jar ~/vnu.jar --also-check-css some-directory-name/
To check all documents in a particular directory as SVG:
java -jar ~/vnu.jar --force-svg some-directory-name/
To check all documents in a particular directory as SVG, but skip any documents
whose names don’t end with the extension .svg:
java -jar ~/vnu.jar --skip-non-svg some-directory-name/
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:
java -jar ~/vnu.jar --also-check-svg some-directory-name/
To check a Web document:
java -jar ~/vnu.jar _URL_
example: java -jar ~/vnu.jar http://example.com/foo
To check standard input:
java -jar ~/vnu.jar -
example: echo '<!doctype html><title>...' | java -jar ~/vnu.jar -
When used from the command line as described in this section, the vnu.jar
executable 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 message 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]
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 vnu.jar 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]
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 vnu.jar version number.
The Nu Html Checkerーalong with being usable as a standalone command-line clientーcan be run as an HTTP service, similar to checker.html5.org, html5.validator.nu, and validator.w3.org/nu, for browser-based checking of HTML documents over the Web. To that end, the checker is released as two separate packages:
vnu.jarfor deploying the checker as a simple self-contained servicevnu.warfor deploying the checker to a servlet container such as Tomcat
Both deployments expose a REST API that enables checking of HTML documents from
other clients, not just web browsers. And the vnu.jar package also includes a
simple HTTP client that enables you to either send documents to a
locally-running instance of the checker HTTP serviceーfor fast command-line
checkingーor to any remote instance of the checker HTTP service running anywhere
on the Web.
The latest releases of the vnu.jar and vnu.war packages are available from
the validator project at github. The following are detailed instructions on
using them.
Note: Replace "~/vnu.jar" or "~/vnu.war" below with the actual paths to those files on your system.
To run the checker as a standalone service (using a built-in Jetty server), open
a new terminal window and invoke vnu.jar like this:
java -cp ~/vnu.jar nu.validator.servlet.Main 8888
Then open http://localhost:8888 in a browser. (To have the checker listen
on a different port, replace 8888 with the port number.)
You’ll see a form similar to validator.w3.org/nu that allows you to enter the URL of an HTML document and have the results for that document displayed in the browser.
Note: If you get a StackOverflowError error when using the vnu.jar file,
try adjusting the thread stack size by providing the -Xss option to java:
java -Xss512k -cp ~/vnu.jar nu.validator.servlet.Main 8888
To run the 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/.
Note: You may want to customize the /WEB-INF/web.xml file inside the WAR
file (you can use any ZIP-handling program) to modify the servlet filter
configuration. For example, if you wanted to disable the inbound-size-limit
filter, you could comment out that filter like this:
<!--
<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>
-->
You can also use vnu.jar from the command line to either send documents to a
locally-running instance of the checker HTTP serviceーfor fast command-line
checkingーor to a remote instance anywhere on the Web.
To check documents locally, do this:
-
Start up the checker as a local HTTP service, as described in the Standalone web server section.
-
Open a new terminal window and invoke
vnu.jarlike this:java -cp ~/vnu.jar nu.validator.client.HttpClient FILE.html...
To send documents to an instance of the checker on the Web, such as html5.validator.nu/, use the nu.validator.client.host and nu.validator.client.port options, like this:
java -cp ~/vnu.jar -Dnu.validator.client.port=80 \
-Dnu.validator.client.host=html5.validator.nu \
nu.validator.client.HttpClient FILE.html...
Other options are documented below.
When using vnu.jar for sending documents to an instance of the checker HTTP
service for checking, you can set Java system properties to control
configuration options for the checker behavior.
For example, you can suppress warning-level messages and only show error-level
ones by setting the value of the nu.validator.client.level system property to
error, like this:
java -Dnu.validator.client.level=error\
-cp ~/vnu.jar nu.validator.client.HttpClient FILE.html...
Most of the properties listed below map to the validator.nu common input parameters documented at github.com/validator/validator/wiki/Service:-Common-parameters.
Specifies the hostname of the checker for the client to connect to.
default: "127.0.0.1"
Specifies the hostname of the checker for the client to connect to.
default: "8888"
example: java -Dnu.validator.client.port=8080 -jar ~/vnu.jar FILE.html
Specifies the severity level of messages to report; to suppress
warning-level messages, and only show error-level ones, set this property to
"error".
default: [unset]
possible values: "error"
example: java -Dnu.validator.client.level=error -jar ~/vnu.jar FILE.html
Specifies which parser to use.
default: "html"; or, for *.xhtml input files, "xml"
possible values: [see information at URL below]
https://github.com/validator/validator/wiki/Service-%C2%BB-Common-params#parser
Specifies the encoding of the input document.
default: [unset]
Specifies the content-type of the input document.
default: "text/html"; or, for *.xhtml files, "application/xhtml+xml"
Specifies the output format for messages.
default: "gnu"
possible values: [see information at URL below]
https://github.com/validator/validator/wiki/Service-%C2%BB-Common-params#out
Specifies whether ASCII quotation marks are substituted for Unicode smart
quotation marks in messages.
default: "yes"
possible values: "yes" or "no"
Specifies the connection timeout.
default: 5000
possible values: number of milliseconds
example: -Dnu.validator.servlet.connection-timeout=5000
Specifies the socket timeout.
default: 5000
possible values: number of milliseconds
example: -Dnu.validator.servlet.socket-timeout=5000
You can pull the checker from the https://hub.docker.com/r/validator/validator/ repo at Docker Hub.
To pull and run the latest version of the checker:
docker run -it --rm -p 8888:8888 validator/validator:latest
To pull and run a specific Docker-Hub tag/version of the checker — for example,
the 17.11.1 version:
docker run -it --rm -p 8888:8888 validator/validator:17.11.1
To run the checker with a connection timeout and socket timeout different than
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 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 checker such that you can
open http://localhost:8888/ in a Web browser to use the checker Web UI.
-
Make sure you have git, python, and JDK 8 or above installed.
-
Set the
JAVA_HOMEenvironment variable:export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64 <-- Ubuntu, etc.
export JAVA_HOME=$(/usr/libexec/java_home) <-- MacOS
-
Create a working directory:
-
Change into your working directory:
cd validator
-
Start the build script:
python ./build/build.py all
The first time you run the build script, you’ll need to be online and the build will need time to download several megabytes of dependencies.
The steps above will build, test, and run the checker such that you can open
http://localhost:8888/ in a Web browser to use the checker Web UI.
Use python ./build/build.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 ./build/build.py build(to build only) -
python ./build/build.py build test(to build and test) -
python ./build/build.py run(to run only) -
python ./build/build.py jar(to compilevnu.jar)