The following serves as an index of a range of web-based tools, browser extensions, command-line tools, scripts, and bookmarklets. It is not complete; it might lack some important tools; but many tools come with my endorsement, and the promise to also serve others well.
(By the way, my UITest.com site is a hub for web-based testing tools, generators, and anything else web-based that’s useful for web developers and designers. You can find many of the tools listed in this book and more there.)
Accessibility Analysis (Gecko browser extension) (https://mzl.la/2cqOkkH)
Accessibility Check (AATT; Automated; command-line tool) (https://github.com/paypal/AATT)
Accessibility Check (FAE) (http://fae20.cita.illinois.edu/)
Accessibility Check (WAEX) (http://www.it.uc3m.es/vlc/waex.html)
Accessibility Check (WAVE 3.0) (http://wave.webaim.org/)
Accessibility Developer Tools (WebKit browser extension) (http://bit.ly/2cI92xl)
Accessibility, HTML, and Link Check (WebKit and Gecko browser extension) (https://www.totalvalidator.com/)
Accessibility Linter (http://accesslint.com/)
Accessibility Visualization (script) (https://github.com/Khan/tota11y)
AES Encrypter (https://www.infoencrypt.com/)
Android Emulators (http://www.manymo.com/emulators)
ARIA Validator (WebKit browser extension) (http://bit.ly/2cqQccO)
Availability Check (CurrentlyDown.com) (http://www.currentlydown.com/)
Availability Check (Is It Down Right Now) (http://www.isitdownrightnow.com/) ...