HTML Tidy seems like a powerful tool although I am having a hard time to find from their docs whether they do simple validation (I guess it does given that you ask the question).<p>This html5validator gives you a simple yes&#x2F;no answer whether some files are HTML5 valid. It is based on the same backend that powers <a href="https:&#x2F;&#x2F;html5.validator.nu&#x2F;" rel="nofollow">https:&#x2F;&#x2F;html5.validator.nu&#x2F;</a>.<p>It can be integrated in continuous integration. The README contains example configurations for TravisCI and CircleCI.