There are many free tools for testing the accessibility of web sites and web applications, and we've divided them into the following categories.
General ItemBrowser Extensions
There are many browser extensions that can be useful in testing the accessibility of web pages.
General ItemColor Contrast Checking Tools
While most general-purpose accessibility testing tools will notify you of problems with color contrast, and sometimes even suggest a better color combination, they can't catch everything. In some cases, you will have to find out what the relevant color values are and enter them in another tool to see if they meet contrast requirements.
General ItemSite Crawling Accessibility Testing Tools
Some tools will perform automated accessibility scans of entire site. Here are some good free ones.
General ItemSoftware Applications
Some software applications, either ones that must be installed separately or utilities that come with the operation system, can be used to test the accessibility of web pages.
General ItemBuilt-In Accessibility Checkers
There are accessibility checkers or tools built into some popular browsers and productivity software.
General ItemCommand Line Developer Tools
For those developers who are really responsible for the nuts and bolts of coding, there are command line tools that can be used to test the accessibility of web pages.