By Sarah Horton and David Sloan — There is a range of assistive technologies that support user accessibility needs relating to access to content, including providing alternative ways to output content and adapting content to better address user accessibility needs. These are mainly software‑based solutions provided through dedicated applications and operating system settings and adaptations; hardware devices also exist to support access to content.
Text‑to‑Speech
For people with accessibility needs relating to significant sight loss, assistive technology can provide an alternative to the visual channel. Perhaps the most widely recognized example is screen reader software, which provides text‑to‑speech output of content along with a powerful set of keyboard commands to allow for flexible navigation through content. Examples of standalone screen reading software include:
- For Windows, JAWS (a commercial product) and NVDA (an open‑source product) are standalone screen reading applications. Microsoft provides Narrator as a screen reading application that comes as standard with Windows, although at the time of writing, Narrator provides more limited capability than JAWS and NVDA.
- For macOS, iOS, and iPadOS, Apple provides VoiceOver as a standard feature of the operating system.
- For Android, Google provides TalkBack as a standard feature of the operating system.
- On Linux, Orca is an open‑source screen reader.
- A version of JAWS is also available to run on Windows‑ and Android‑based kiosk platforms.
WebAIM, a non‑profit accessibility organization based at Utah State University, regularly runs a Screen Reader User Survey, reporting on usage statistics of screen readers across different platforms, along with a range of additional useful data on behaviors and preferences. These surveys, conducted approximately every two years, have provided fascinating insights into trends in screen reader use over time. Their 2021 survey reported JAWS, NVDA, and VoiceOver as the three most commonly used screen readers.
In addition to dedicated screen reading applications, there is a category of application that includes text‑to‑speech functionality, among other features. For example, reading assistance software supports people who have functional vision but have accessibility needs that require assistance in reading and comprehending text content. For example, someone with dyslexia may prefer to highlight a block of text and have it read aloud to reduce the effort required to visually process the text.
Non‑visual interaction with digital applications involves a very different interaction paradigm to visual exploration of a user interface and its content.
Tactile Output
Some assistive technologies that provide an alternative to the visual channel do so by providing tactile output. These may be used alongside or instead of a screen reader. Tactile printouts or models of content can provide accessible versions of graphic content such as diagrams and maps. Tactile labels and controls on a kiosk or other hardware device can make non‑visual operation easier, as can haptic cues like vibration, for example, on watches and smartphones. For people who are deafblind, some form of tactile interaction and output is necessary to work with digital products.
As a more powerful and flexible solution, refreshable braille displays are hardware devices controlled by screen reader software to present screen content as physical braille characters. They rapidly refresh to support quick reading of screen content and vary in size depending on how many characters they can display at one time. Larger braille displays can present up to 80 characters at a time, but have limited portability, so tend to be attached to a standard keyboard for a PC or laptop. Smaller braille displays present fewer characters at one time but are portable and may be linked to a smartphone or other device using a wireless connection. Some braille displays also allow users to create content, using custom keypads to quickly generate braille content. For people who use braille, these devices can significantly improve efficiency of reading and writing.
Magnification
A range of assistive technology is available to customize an interface’s visual display to make it easier for people to perceive content. Screen magnification software can magnify the content of the screen to many times the default text size, giving users power over levels of zoom and the means to control them. Since zooming reduces the amount of content shown on screen at any given time, screen magnification software also has functionality to support orientation and tracking around a screen, helping readers maintain focus, locate content, and improve reading performance. Screen magnification software may also include other display customization options and text‑to‑speech capabilities.
On tablets and mobile devices, functionality to zoom or magnify screen content or change text size is embedded with the operating system and is widely used to make content easier to read and also to address the limitations of a smaller screen. Hardware solutions also exist for magnifying content, for example, through use of a document camera or magnifying glass.
Display Modifications
Assistive technology features to support reading difficulties or reduced vision include hardware, software, and operating system settings that allow users to:
- Set a large text size and reflow content and functionality to accommodate larger text.
- Change color schemes, for example, inverting colors so that content is shown in light text on a dark background or applying a high‑contrast color palette to increase readability.
- Adjust the appearance of the focus indicator.
- Change the appearance of the mouse pointer to make it easier to track.
- Reduce brightness and color contrast to reduce eye strain and stimulation.
Note that along with AT to augment the visual channel, like magnification and display adjustments, some people with vision or cognitive accessibility needs may use a screen reader to read out specific screen content. This means you should avoid design decisions that assume all screen reader users cannot see the screen.
From Horton, S., & Sloan, D. (2024). What Every Engineer Should Know About Digital Accessibility. CRC Press, Boca Raton, Florida.
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