W3C Markup Validation Service - Validates HTML markup of web pages, one at a time.
ArchitectUI - Modern dashboard template for bootstrap 4
Total Validator - Total Validator can check your website to help ensure that it is accessible, uses valid HTML and CSS, has no broken links, and is free from spelling mistakes.
Flatlogic - Business Software: AI-Driven Solutions at Speed.
Rocket Validator - Site-wide Accessibility and HTML validation made easy. With a single click, Rocket Validator will check thousands of web pages on your site for Accessibility and HTML conformance, producing a detailed, actionable report on seconds.
PlainAdmin - PlainAdmin is an Open-source freemium Bootstrap 5 based vanilla JS multipurpose admin template comes with - all essential dashboard components, pages, UI elements, charts, graphs, libraries and everything you may need for a data-rich backends.