Adobe Flash is an animation technology that allows web developers to build dynamic content featuring multimedia and interactive applications. Flash content downloads quickly and can run on any browser that supports it and is equipped with the Adobe Flash Player plug-in.
Initially, Flash content was not accessible to all users, including screen reader users, mouse-free users, people who are deaf or hard of hearing, and other people with disabilities. However, over a number of years, first Macromedia, and then Adobe, added accessibility features. For example, many Flash video players added support for closed captions, and the Flash authoring environment added functionality that could improve the experience for screen reader users and keyboard-only users in the Windows operating system. However, these features did not extend to other operating systems, nor were they comprehensive even in the Windows environment. For example, Flash does not support Windows high contrast mode nor users' text size settings.
In 2016, Adobe rebranded Flash as Adobe Animate CC, which continued to have the same basic level of accessibility support as Flash, as well as the same limitations. For additional information see Adobe's Flash Accessibility page.