Digital Design

Visuals and Alternatives
Understanding Alternative Text

Image: Laptop with 4 images on ina document on the screen.


When words and images are not accessible, many people are excluded. Accessible images provide equal access to information and the opportunity to identify, understand, navigate, interact and contribute to the digital world. When images on websites, web applications, mobile apps, video, PDFs and office documents are developed and designed with accessibility in mind, everyone can access information without barriers.

Developing an Understanding

Image descriptions are known as “alternative text” or “alt text”, because they are textual alternatives to images. Alternative text is a short, written description of an image that makes images accessible for people who are blind or have low vision and use screen readers to access information on websites, PDF, Word and PowerPoint documents.

Screen readers cannot read images, only text. The screen reader reads aloud the information on a computer screen and will tell the user there is an image present. If alt text is provided, the screen reader will read it aloud. If there is no alternative text, you will know there is an image but you won’t be told anything about that image.

In the video below check out how a screen reader interprets different types of alt text and images without alt text.

Deepening your Understanding

Screen readers are software/programs that convert text into synthesized speech. Screen readers read all the text from the top of the screen to the bottom, one line at a time. You can also use the keyboard to navigate and move around the screen.

There are a number of screen reading software available.

JAWS logo

Job Access with Speech (JAWS) was developed for computer users whose vision loss prevents them from seeing screen content or from using a mouse. JAWS provides speech as well as braille output for most of the applications on a PC computer screen (Freedom Scientificopen new window, n.d.).

Apple Voice Over logo

VoiceOver is a screen reader that is built into Apple Inc.'s OS X, iOS, tvOS, watchOS, and iPod operating systems. VoiceOver users can access their Mac or iOS device based on spoken descriptions or by using the keyboard. VoiceOver offers auditory descriptions of onscreen elements and supports more than 30 languages, including multiple voice options (Appleopen new window, 2017).

NonVisual Desktop Access (NVDA) logo

NonVisual Desktop Access (NVDA) open new window is a free screenreader for computers that are using Windows. NVDA can be installed on to a computer or it can run from and USB and supports web browsers, email, internet chatting, and office programs including Word and Excel. NVDA has a built-in speech synthesizer for English and 43 other languages and can offer support for braille displays (NonVisual Desktop Access, 2017).