Accessibility guide

Alt Text Guide: Writing Good Alternative Text

Alt text (alternative text) is the written description of an image that screen readers announce and that appears when an image fails to load. Getting it right is one of the most basic accessibility tasks, yet missing alt text remains one of the most common failures on the web. This guide explains how to write good alt text and when to leave it empty.

Reviewed by the EAA Navigator team

TL;DR

  • Alt text describes the purpose and content of an image for people who cannot see it.
  • Informative images need alt text that conveys the same information the image gives a sighted user; decorative images should have empty alt text so screen readers skip them.
  • Missing alt text is one of the most common failures online: 55.5% of home pages had missing alternative text in the WebAIM Million 2025.
  • Good alt text is concise and describes meaning, not appearance for its own sake — and it never starts with "image of".
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In this guide

What this covers

  • What alt text is and where it is used.
  • The difference between informative and decorative images, and how to treat each.
  • How to write alt text that conveys an image’s purpose, not just its appearance.
  • Special cases: images of text, functional images (links and buttons) and complex images such as charts.

What matters

How to write it well

  • Informative images: write alt text that gives the same information a sighted user gets, in as few words as needed. For a product photo, describe the product; for a chart, summarise the point it makes.
  • Decorative images: use empty alt text (alt="") so screen readers skip them. A decorative flourish with a description just adds noise.
  • Functional images: when an image is a link or button, the alt text should describe the action or destination, not the picture — for example "Search" rather than "magnifying glass".
  • Keep it concise and avoid redundancy: do not start with "image of" or "picture of", and do not repeat text that already sits next to the image.
  • Images of text: avoid them where possible; if unavoidable, the alt text must contain the same words as the image.

Across web accessibility, Level AA of WCAG 2.2 is the working target, and for the EU it is incorporated into the harmonised standard EN 301 549.

What to do

What to do next

  1. For every image, decide whether it is informative, decorative or functional — that decision drives the alt text.
  2. Write concise alt text for informative images that conveys their purpose, and use empty alt (alt="") for purely decorative ones.
  3. For images that are links or buttons, describe the action or destination rather than the graphic.
  4. Remove "image of" / "picture of" prefixes and avoid repeating adjacent caption text.
  5. Audit your key pages for missing alt attributes — it is one of the most common failures and one of the easiest to fix.

For the standard itself, see the WCAG explainer; to put it into practice, work through the WCAG 2.2 AA checklist.

FAQ

Common questions

What is alt text?
Alt text, or alternative text, is a written description of an image. Screen readers announce it to people who cannot see the image, and browsers show it when an image fails to load. It is set with the image’s alt attribute.
Should every image have alt text?
Every image needs an alt attribute, but not every image needs a description. Informative images need alt text that conveys their meaning; purely decorative images should have empty alt text (alt="") so screen readers skip them.
How long should alt text be?
As short as possible while still conveying the image’s purpose — usually a sentence or less. If an image needs a long description, such as a complex chart, provide a short alt text and put the full explanation in nearby text.
How common is missing alt text?
Very common. The WebAIM Million 2025 found missing alternative text on 55.5% of the top one million home pages, making it one of the most frequent accessibility failures on the web — and one of the simplest to fix.

Make your site accessible

Start with the WCAG 2.2 AA checklist, then work through the guides to fix what you find.

Get the WCAG ChecklistTry the contrast checker

This is guidance, not legal advice

This guide is here to help you understand web accessibility and how WCAG, the EAA and the ADA apply in practice. It is not legal advice. For decisions specific to your business, confirm with the official sources we link or a qualified adviser.

Sources

  1. [1]Web Content Accessibility Guidelines (WCAG) 2.2 (W3C Recommendation)retrieved 9 Jun 2026
  2. [2]WCAG overview (W3C Web Accessibility Initiative)retrieved 9 Jun 2026
  3. [3]Directive (EU) 2019/882 — European Accessibility Act (EUR-Lex)retrieved 9 Jun 2026
  4. [4]EN 301 549 v3.2.1 — harmonised ICT accessibility standard (ETSI)retrieved 9 Jun 2026
  5. [5]US DOJ ADA Title II web accessibility rule fact sheetretrieved 9 Jun 2026
  6. [6]WebAIM Million 2025 — accessibility of the top 1,000,000 home pagesretrieved 9 Jun 2026
  7. [7]Overlay Fact Sheet — why overlays do not deliver complianceretrieved 9 Jun 2026

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Alt Text Guide: Decorative vs Informative Images | EAA Navigator · EAA Navigator