What does alt text look like in HTML?

It is the alt attribute inside the img tag: <img src="shoe.jpg" alt="Red trail running shoe, side view">. Nothing shows on screen while the image loads correctly — the text exists for screen readers, search engines and the moments the image fails.

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Definition

What Is Alt Text?

Q: How long should alt text be?

Between roughly 8 and 125 characters — most good alt text lands at 5 to 15 words. Under 8 characters it rarely describes anything; over 125, screen readers on some platforms truncate it and the description loses focus. Our ALT Quality Score uses exactly those two thresholds.

Q: Do icons need alt text?

Only when they carry meaning on their own. An icon that duplicates adjacent text (a magnifier next to the word “Search”) is decorative: give it an empty alt. An icon that is the only signal (a lone trash icon button) needs an alt that names the action, not the drawing: “Delete”, not “trash can icon”.

Q: Is alt text the same on Instagram or Bluesky?

The principle is identical — a text description attached to an image — but each platform has its own field and rules. This guide covers alt text on websites, where you control the HTML.

Definition, HTML syntax, ideal length and what it changes for SEO.

Alt text (alternative text) is a written description of an image, stored in the alt attribute of the HTML <img> tag. Screen readers read it aloud, search engines use it to understand the image, and browsers display it when the file fails to load. Good alt text runs 5 to 15 words.

Syntax

What alt text looks like in the code

The attribute lives inside the image tag: <img src="shoe.jpg" alt="Red trail running shoe, side view">.

Nothing shows on the page itself. The text waits in the markup for whoever needs it: a screen reader, a search engine crawler or a browser stuck with a broken image.

Why it matters

Why is alt text important?

Accessibility

Screen reader users hear the alt text in place of the image. WCAG 2.1, success criterion 1.1.1, requires a text alternative for every informative image, and the European Accessibility Act applies since 28 June 2025.

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SEO

Alt text is the main signal search engines use to understand what an image shows. It also feeds rankings in Google Images.

Robustness

When a file breaks or a connection drags, the browser prints the alt text where the image should be. Visitors still get the information.

Length

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How long should alt text be?

Aim for 8 to 125 characters, which lands around 5 to 15 words. Below 8 characters the description carries too little to be useful. Past 125, some screen readers truncate the text mid-sentence.

Those two thresholds are exactly what our checker tests, along with generic wording and duplicates.

2,449

images audited in 2026 for our benchmark

25.2%

had no alt text at all

67.6/100

average alt quality score

median score across audited images

Comparison

Alt text vs title text vs caption

Three fields with different jobs. Only one of them matters for accessibility.

Attribute	Who gets it	Required?	SEO weight
Alt text	Screen readers, search engines, anyone whose image fails to load	Yes for informative images (WCAG 2.1, criterion 1.1.1)	Direct
Title	Tooltip on hover; skipped by most screen readers	No	Negligible
Caption	Visible to every visitor, under the image	No	Indirect

FAQ

Frequently asked questions

What is alt text in SEO?

It is the main way search engines understand image content, and it counts toward image rankings. Stuffing keywords into it backfires: the text stops describing the image and both accessibility and rankings suffer. Write for the reader first.

Do icons need alt text?

A decorative icon that repeats the text next to it takes an empty alt (alt=""). A meaningful icon, like a trash can that deletes a file, needs an alt that names the action, "Delete" for example.

Is alt text the same on Instagram or Bluesky?

The principle carries over: describe the image for people who will hear it instead of seeing it. Each platform then places the field its own way, with its own length limits.

Where can I see good alt text examples?

We keep a full page of alt text examples, good and bad, sorted by image type. The patterns come from real audits.

Another question?

The full FAQ covers the checker, the score, the plugin and how your data is handled.

Now check your own images

Paste a URL into the free checker and every image comes back scored out of 100. The full method sits in our alt text benchmark.

Alt text audit and bulk management for WordPress. Quality score, bulk fixing, accessibility. Built in France by Lyode.