Episode 4: Understandable – all 21 rules

Welcome to WCAG made simple. This episode is about principle 3: Understandable. Text and behaviour must be clear and predictable. Mistakes are easy to avoid and to fix. This principle has 21 rules. We will go through them in order.

Guideline 3 point 1: Readable. Language is declared and text is understandable.

3 point 1 point 1, Language of Page. Level A. The main language of the page is set in code. Only then does a screen reader use the right pronunciation – otherwise English sounds as if read by a German voice.

3 point 1 point 2, Language of Parts. Level double A. Passages in a different language are also marked in code.

3 point 1 point 3, Unusual Words. Level triple A. Jargon, idioms and unusual words are explained.

3 point 1 point 4, Abbreviations. Level triple A. Abbreviations are expanded or explained.

3 point 1 point 5, Reading Level. Level triple A. If text is harder to read than expected after about 9 years of school, there is a simpler version or a summary.

3 point 1 point 6, Pronunciation. Level triple A. Where the meaning of a word depends on its pronunciation, the pronunciation is given.

Guideline 3 point 2: Predictable. Pages behave the way people expect.

3 point 2 point 1, On Focus. Level A. Just because an element receives focus, nothing unexpected happens: no page change, no new window, no submit.

3 point 2 point 2, On Input. Level A. Selecting or typing something does not automatically cause anything unexpected – unless people were told beforehand.

3 point 2 point 3, Consistent Navigation. Level double A. Navigation that appears on several pages is in the same order everywhere.

3 point 2 point 4, Consistent Identification. Level double A. Things with the same function are named and labelled consistently everywhere.

3 point 2 point 5, Change on Request. Level triple A. Major changes happen only when someone triggers them – or they can be turned off. No automatic redirects, no unrequested new windows.

3 point 2 point 6, Consistent Help. Level A. If help options such as contact details, chat or FAQs appear on several pages, they are in the same order relative to other content on each page.

Guideline 3 point 3: Input Assistance. Forms help people avoid and correct mistakes.

3 point 3 point 1, Error Identification. Level A. When input is wrong, text says which field is affected and what is wrong. A red border alone is not enough.

3 point 3 point 2, Labels or Instructions. Level A. Every input has a visible label. If a specific format is required, it is stated beforehand.

3 point 3 point 3, Error Suggestion. Level double A. Error messages do not just say something is wrong, they also say how to get it right.

3 point 3 point 4, Error Prevention (Legal, Financial, Data). Level double A. For important actions such as purchases, contracts, test answers or deleting data, people can review, correct or undo their input.

3 point 3 point 5, Help. Level triple A. Help for inputs and tasks is available right where it is needed.

3 point 3 point 6, Error Prevention (All). Level triple A. For all forms – not just important ones – people can review, correct or undo their input.

3 point 3 point 7, Redundant Entry. Level A. What someone has already entered in a process does not have to be typed again. It is pre-filled or offered for selection.

3 point 3 point 8, Accessible Authentication (Minimum). Level double A. Logging in does not require a memory or thinking test: no typing a password from memory, no puzzle – unless there is an alternative or help. Still allowed at this level: recognising objects or content you provided yourself.

3 point 3 point 9, Accessible Authentication (Enhanced). Level triple A. Logging in works with no memory or thinking task at all – not even recognising objects or personal pictures.

Those were all the rules for the principle Understandable. On the website you will find an example and a practical tip for every rule. Thank you for listening.