There is a new tool from Microsoft/Axe partnership. Microsoft is one of the leaders in Accessibility. Partnering with Axe (Deque), the tool not only has a fast checker, it shows both on the site and in the report where the problems are, links to exact WCAG rules and has guidelines how to fix. All Open Source.
Chrome extension:
https://chrome.google.com/webstore/detail/accessibility-insi...