Install vnu with Homebrew

Project links

• Homepage
• Upstream docs
• Package manager page

Commands and aliases

• vnu

Project history

The project grew out of the HTML5-era validator.nu checker work and became the backend behind `html5.validator.nu`, `validator.w3.org/nu/`, and the HTML5 facet of the legacy W3C validator. A W3C validator mailing-list announcement in August 2014 described a new Nu Markup Checker release that packaged the same backend as a portable `vnu.jar` and as a WAR file for servlet containers.

The current README describes the project as the Nu Html Checker and says release 20.6.30, dated 30 June 2020, was the final major version-numbered release; after that, users are directed to the production-ready release named `latest`. The same README documents a broad packaging model: standalone runtime images, `vnu.jar`, `vnu.war`, a container image, and integrations with build tools.

Adoption history

vnu's adoption is tied to the web standards ecosystem rather than to a single application. It is the checker behind a public W3C validation endpoint, appears in frontend build workflows through Grunt, Gulp, Maven, npm, containers, and direct CLI use, and is deliberately described by its own about page as an evolving checker rather than a formal pass/fail certification service.

How it is used

Developers use `vnu` to catch unintended mistakes in HTML, CSS, and SVG, either by running the jar or native runtime against files, directories, or URLs, or by starting a local/server-side HTTP checker. The README's examples cover command-line batch checking, a standalone web server, servlet deployment through a WAR file, an HTTP client for a local or remote checker service, and containerized operation.

Why package nerds care

For package users, vnu is important because it turns the constantly evolving web-platform conformance checker into a local, scriptable artifact. That makes it usable in CI, static-site builds, editor tooling, and regression suites without sending every document to a public validator service.

Timeline

• 2014-08-27: W3C announces a Nu Markup Checker release with `vnu.jar` batch checking and WAR deployment.
• 2018: GitHub releases show standalone jar and WAR distributions used for command-line and service deployments.
• 2020-06-30: Release 20.6.30 becomes the final major version-numbered release.
• 2021: The project publishes a GitHub container package for the checker.
• Present: Upstream directs production users to the continuously updated release named `latest`.

Related projects

• Related projects and surfaces include validator.nu, W3C Markup Validation Service, `validator.w3.org/nu`, the validator.nu HTML parser, and build-tool front ends such as Grunt, Gulp, and Maven HTML-validation plugins.

Sources

• Nu Html Checker README: https://raw.githubusercontent.com/validator/validator/master/README.md
• Nu Html Checker about page: https://validator.github.io/validator/site/nu-about.html
• Nu Html Checker releases: https://github.com/validator/validator/releases
• W3C www-validator announcement, 2014-08-27: https://lists.w3.org/Archives/Public/www-validator/2014Aug/0026.html