- WebAIM color contrast checker compares two hex colors and tells you whether they meet WCAG AA and AAA contrast thresholds.
- Snook's color contrast analyzer lets you adjust RGB and HSV values and reports contrast compliance interactively.
- NC State palette accessibility evaluator lets you compare contrast between three or more colors for WCAG AA or AAA compliance.
- Color Safe is a guide for choosing colors that meet WCAG contrast thresholds.
- Color Contrast Analyzer is a desktop application for contrast checking that also simulates different forms of color impairment.
- Color Oracle is another desktop application for simulating color impairment on your entire screen.
- Daltonize is a collection of bookmarklets that simulate the three most common forms of color impairment (protanopia, deuteranopia, and tritanopia) on any web page.
- colourblind is another simulation tool similar to Daltonize, but with more options (protanopia, protanomaly, deuteranopia, deuteranomaly, tritanopia, tritanomaly, achromatopsia, and achromatomaly) in a single bookmarklet.
- postcss-colorblind is a CSS build tool that modifies colors in your CSS to simulate four common impairment groups.
Accessibility Review Tools
These tools can be used to test sites for Section 508 and WCAG compliance in browser:
- achecker is an accessibility reporter for HTML only.
- Google's Accessibility Developer Tools is a Chrome plugin for running basic accessibility tests from the comfort of your browser.
- Web Accessibility Toolbar (WAT) is an IE tool that has been developed to aid manual examination of web pages for a variety of aspects of accessibility. It is used by DHS's Trusted Tester program.
- WAVE is an accessibility auditor and browser extension with document inspection features.
- The W3C maintains a comprehensive list of web accessibility evaluation tools.
Automated testing tools can help you find some of the more common accessibility mistakes quickly, however no automated tool can detect all accessibility issues. A recent experiment by the UK's Government Digital Service found that the best automated tools only caught about 40 percent of the errors on a test site; some of the most popular tools caught less than 20 percent. Whatever automated tool you use, be sure to also do manual testing. These tools can be used in automated tests and with continuous integration tools to help you ensure that your sites remain accessible throughout the development process:
- AccessLintCI runs accessibility tests in CircleCI builds and comments on GitHub pull requests with new accessibility issues. See more information on how to add this to an 18F site here.
- ra11y is a Ruby-based accessibility testing tool tuned for use with Jekyll and static sites.
- webalin is a Python-based 508 compliance linter for HTML.