3.1.5 Reading Level
Official description of the success criterion
When text requires reading ability more advanced than the lower secondary education level after removal of proper names and titles, supplemental content, or a version that does not require reading ability more advanced than the lower secondary education level, is available.
What to do?
Ensure content is readable and understandable, ideally at a lower secondary education level.
You can provide visuals to help explain the content. Sometimes icons can make things easier to understand. Of course, it requires the icons to be understandable.
You can provide a spoken version of the text. There are quite a few paid services like ReadSpeaker available that won't require you to record the spoken versions.
Why is it important?
Makes content accessible to users with varying levels of literacy.
Common pitfalls
Sometimes we make our content more complicated than it needs to be. At least I was taught in school that we are supposed to use fancy words and that we shouldn't repeat the same word but instead use synonyms. Well, when accessibility is concerned, those rules can be forgotten, at least to an extent.
How to test for it?
For text in English, there is the Hemingway Editor you can use to check for the reading level of text content. The tool will let you know if a sentence is hard or very hard to read. It will also suggest simpler alternatives to words that might be unnecessarily complicated.