Make dense text easier to read
G153 is about the writing rather than the markup. W3C's advice is concrete. One topic per paragraph, the simplest sentence form the meaning allows, and sentences no longer than the usual secondary-school length, which W3C puts at around 25 words in English. Split the long ones. This is a sufficient technique for 3.1.5 Reading Level, a Level AAA rule whose test is whether the text needs reading ability beyond lower secondary education. Clear that bar and no supplement or alternative version is needed at all. Readability formulas are a decent way to triage a site and a poor way to judge one, because they count syllables and sentence length and cannot tell whether the sentence made sense.
How we find it in an audit
Our reviewers read the pages that carry consequences, which usually means eligibility, terms, safety and money. We score them for triage, then read them properly, because a formula will happily approve a short sentence that means nothing. Where the formal wording has to stay, we look for a plain-language version alongside it rather than instead of it.
How affected users experience it
Dense text is a barrier for people with cognitive and learning disabilities, for readers working in a second language, and for anyone reading through speech, where a 60-word sentence has to be held in memory to the end. Nobody reports this as an accessibility problem. They report it as not qualifying for the benefit, or not understanding the form, which is the same outcome arriving under a different name.
Passes vs. fails
Passes
The same rules are rewritten with short sentences, everyday words and one idea per paragraph, with the formal legal text linked for anyone who needs it.
Fails
A benefits eligibility page is written in 60-word sentences of legal boilerplate, at postgraduate reading level.
Other ways to satisfy this rule
5 guides on this site are filed under 3.1.5 Reading Level. W3C lists this one as sufficient for that rule on its own. Implement it correctly, in a way your readers' software actually supports, and the rule is met.
This guide is our interpretation of W3C technique G153: Making the text easier to read. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.