The 125-character rule: where it comes from and when to break it

Ask five people why alt text should stay under 125 characters and you'll get five confident answers, most of them wrong. The most common one: "screen readers cut it off after that." That's not quite what happens, and the real story is worth knowing before you decide when to ignore the rule.

Where the number actually comes from

The 125-character figure traces back to older versions of JAWS, a widely used screen reader, which processed alt text in chunks of roughly 125 characters. Rather than cutting text off, JAWS split long alt text into multiple "graphics," each carrying its own chunk, picking up where the last one left off. Nothing was lost — but it meant one image could get announced as several, which is its own kind of confusing.

Why the rule survives anyway

Even with truncation off the table, 125 characters holds up as a decent target for a different reason: a screen reader user can't skim alt text the way a sighted person skims a sentence. They hear it start to finish, or not at all. A description that runs long asks for more patience than most people have for a single image, especially when there are a dozen more in the same feed.

The second version loses almost nothing a listener needs and gets there in about five seconds instead of ten.

When to break it on purpose

Some images genuinely need more room: a chart with several data points, a screenshot of a multi-step interface, an infographic carrying real information a viewer would otherwise miss entirely. In those cases, a longer, well-structured description serves the user better than an artificially clipped one. The 125-character number is a target for ordinary photos, not a ceiling that applies to every image regardless of what's actually in it. Use your judgment on what the image needs to communicate, and let the length follow from that — not the other way around.