When testing your website for accessibility issues, you need to use a variety of assistive technologies that most disabled individuals are likely to use when navigating the Internet. This post focuses on screen reader testing specifically, but assistive technologies vary widely by type and brand and should all be considered.
Blind and other visually-impaired users who visit your website or use your app will often use a program called a screen reader that will dictate your site's content to them through a synthesized voice. Although the software is called a "screen reader," these programs frequently do more than just make text audible. They also enable users to navigate the webpage by heading, frame, and other methods.
Because Voiceover is bundled with Macs and NVDA is free to download to Windows users, these two are among the most popular screen readers and therefore are referred to frequently in screen reader studies and testing. JAWS is the most widely-used commercial screen reader, followed by WindowEyes and ZoomText. Fire Vox is a free screen reader that works on Mac and Windows but only works in the Firefox browser, while Orca is a free screen reader for Linux users.
Testing website accessibility using screen readers is an intricate process, and each software can have wildly different results when testing the same websites. This is especially true when comparing mobile and desktop sites; a screen reader that works well on a mobile site might not have the same results on the desktop version. This presents several challenges in both the testing and development aspects, which makes test environments that much more important.
With the rise in visually-impaired users relying on screen readers equally for mobile and desktop use, ongoing screen reader testing is a priority in making websites accessible on both platforms. Mobile operating systems will have differences in input and output, and desktop sites will have varied results from the screen readers depending on the browser being used (and depending on if the browser has WAI-ARIA support).
When testing your website’s accessibility, you need to set up a screen reader test environment to view your site's output in higher detail. JAWS will let you test for 40 minutes at a time while WindowEyes allows for 30 minutes. The more screen readers that you test with, the more reliable your results will be. It’s not feasible to test with each one on the market, but it's prudent to start with the most widely-used programs (most of which are free).
Get comfortable with each program. Turn the screen off and listen to what each screen reader says in each combination of device and browser: Does it make sense? If not, does the text on the page need more breaks, and do images need to be moved?
Ideally, you also want a consultant trained in screen reader testing to help you, along with visually-impaired users who can give genuine feedback for how each combination sounds and if the message you are trying to relay is realized.