Skip to content
You are here: Home » Accessibility » Chapter 14 – Principle 1: Perceivable

Chapter 14 – Principle 1: Perceivable


Thanks for your interest in the Abra kick-off training about the accessibility of apps. My name is Paul van Workum and I am working in the field of app accessibility.

Principle 1: Perceivable

Information should be perceivable for everyone in the way they prefer. For example, someone who is blind cannot see the interface. By making it possible to read the interface, the information can be perceived.

Guideline 1.1: Text Alternatives

Use alt text for images, so screen readers can read what is visually shown.

Guideline 1.2: Time-based Media

Provide a transcript, subtitles or audio description so anyone can perceive media. Media is audio, video or both.

Guideline 1.3: Adaptable

Mark headings as heading, so a screen reader can read that it is a header.

Make sure that besides portrait, also landscape mode is available.

We advise you to implement large text in combination with landscape mode. With both, you probably need a scroll function and all elements should be able to scale.

Guideline 1.4: Distinguishable

Make sure colour isn’t the only way information is conveyed. If for example the state of a tab is only indicated in colour for 1 in 10 men this is not perceivable. Also do not point to “the red button” or use a legenda with colour as the only indicator.

Make sure text can be enlarged. 20% of the users prefer large text. Some are even dependent on this.

Ensure that audio which lasts longer than three seconds can be paused or stopped. Very important for users dependent on their screen reader.

Provide sufficient contrast of elements and text. For some visually impaired people contrast is essential to perceive information.