Understandable · 3.1 Readable
A mechanism must be available to identify the pronunciation of words whose meaning stays ambiguous in context unless the pronunciation is known, such as phonetic spelling beside the word, a glossary with pronunciations, audio clips, or ruby annotations.
Live demo
The same task, done two ways: switch between the version that passes and the one that fails, or put them side by side. Everything in the box is live, so try it with a keyboard, a pointer or a screen reader.
Press Listen on each line in both versions. The passing version gives the pronunciation in the text and uses it in the speech.
Divers find lead near the old mine.
Say lead like "led": it means the metal, not a clue.
Message from your bank. Status: read.
Say read like "red": you have already opened this message.
Divers find lead near the old mine.
Message from your bank. Status: read.
The tools follow the version you last used.
What happened
Why it passes
Each ambiguous word has its pronunciation beside it, and the speech uses it, so you hear "led" for the metal and "red" for a message you have already opened.
Why it fails
Nothing says how to pronounce the words, so the speech has to guess. It may say "leed" or "reed", and then the sentence means something else.
Examples
Four examples, each one running: the usual ways this criterion fails, and code that passes. Listen to them, measure them, or copy the code.
Fails
Live preview
<h2>Divers find lead near the old mine</h2><p>The find was made on Tuesday morning.</p>Lead can be the metal, said "led", or a clue, said "leed". The text does not settle which, and nothing tells the reader how to say it.
Passes
Live preview
<h2>Divers find lead near the old mine</h2><p>Lead (said "led") is the heavy grey metal once dug from this mine. The find was made on Tuesday morning.</p>The first sentence gives the pronunciation straight after the word, so readers know it is the metal before they read on. This is technique G120.
Fails
Live preview
<p lang="ja">この箱には生物が入っています。</p>生物 read as せいぶつ means living things, and read as なまもの means perishable food. Without the reading, the label can be understood either way.
Passes
Live preview
<p lang="ja">この箱には<ruby>生物<rp>（</rp><rt>なまもの</rt><rp>）</rp></ruby>が入っています。</p>The ruby text shows the reading なまもの above the word, which tells the reader the box holds perishable food. The rp brackets appear only where ruby is not supported. This is technique H62.
Why it matters
Screen reader users, people with reading disabilities, and readers of languages such as Japanese or Hebrew, where one written form can have several readings, may otherwise misread a word and misunderstand the sentence.
W3C: Understanding 3.1.6Level AAA
Level AAA is the highest level. It is not required for whole sites, but it is worth meeting where you can.
Where it is required
No law on this site requires Level AAA criteria for whole sites.
How to test
A few concrete steps. Automated tools find some failures; most need a person.
Common failures