CSS HTML Validator

CSS HTML Validator (formerly CSE HTML Validator) is an offline validation tool for HTML/HTML5 and CSS. It also performs accessibility, SEO and link checks, JavaScript linting, PHP checking and spell checking, and includes HTML and CSS editors.

The Windows editions (Home and Professional) have a graphical interface; htmlval is a console version for macOS and Linux, with a free limited edition. The current version is 26.02. It is sold with one-time licences and a free trial.