There are 2 repositories under html-checker topic.
:white_check_mark::octocat: Run htmltest as part of your GitHub Actions workflow
Mirror of the HTML-Validate GitLab repository
CSS HTML Validator is a fast HTML and CSS validator / syntax checker / linter that can also check accessibility, SEO, and more. This project is another way to report issues and feature requests.
Checks for validity of image source references in a html files which use the <img src="./path/to/image"> tag explicitly in the markup.