CSS HTML Validator for Windows, Mac, and Linux is a fast, powerful, highly user configurable, and easy to use web development tool that checks HTML, CSS, SEO, spelling, accessibility (including WCAG 2.0/2.1/2.2), PHP, XHTML, JavaScript, htmx, and links.
CSS HTML Validator includes batch processing (in the Pro edition), integrated HTML/CSS editing, and much more.
It works offline so it's super-fast and your privacy is protected because your documents are not uploaded to a server for checking.
CSS HTML Validator Pro has superior customization features so you can configure the validation to your liking. You can even add your own validator messages, recognize your own HTML elements and attributes, and much more.
Try CSS HTML Validator Pro for Windows free for 200 validations or 30 days, whichever comes first. A FREE limited version of htmlval for Mac and Linux is also available.