The short answer

Alt text is a short written description of an image, added in the alt attribute, that screen readers read aloud. Good alt text says what the image shows or does in context, in one short sentence. Decorative images get an empty alt (alt="") so screen readers skip them.

Key takeaways

  • Describe the purpose of the image in its context, not every pixel.
  • Keep it short: one sentence, usually under 125 characters.
  • Never start with "image of" or "picture of".
  • Decorative images need alt="" (empty), not a missing alt.
  • Images that are links or buttons describe where they go or what they do.

About half of the top one million home pages have images without alt text, according to the WebAIM Million 2026 report. It is one of the most common accessibility problems on the web, and one of the easiest to fix. This guide shows you exactly what to write.

What alt text is and who uses it

Alt text (short for alternative text) lives in the alt attribute of an image: <img src="coat.jpg" alt="Blue wool winter coat with a hood">. People who are blind or have low vision hear it through a screen reader. It also shows when an image fails to load, and search engines and AI assistants read it to understand your page.

The step-by-step method

  1. Ask what the image is for

    Look at the image in its place on the page. Is it there to inform, to decorate, or to act as a link or button? The answer decides what you write.

  2. Write one clear sentence

    Describe what matters for the page. For a product photo: “Blue wool winter coat with a hood, front view.” For a team photo on an About page: “Our five bakers in the kitchen at 5 am.”

  3. Cut the filler

    Remove “image of”, “photo of” and keyword lists. Screen readers already announce that it is an image.

  4. If the image is a link, the alt text says where it goes: “Home” for a logo that links to the home page, “Search” for a magnifying glass button.

  5. Mark decorative images as empty

    Background flourishes, dividers and stock images that add nothing get alt=””. In WordPress, leave the Alternative Text field empty only for these.

  6. Check your pages

    Run a scan to find images with no alt attribute or alt text that looks like a file name, such as “IMG_2041.jpg”.

Examples: bad, better, best

  • Product photo. Bad: “coat”. Better: “Winter coat”. Best: “Blue wool winter coat with a hood, front view.”
  • Chart. Bad: “chart”. Best: “Bar chart: online sales grew from $40,000 in January to $65,000 in June.” If the chart is complex, summarize it in the alt text and put the full data in a table on the page.
  • Logo linking home. Bad: “logo.png”. Best: “Maple Bakery home”.
  • Decorative swirl. Best: alt="".

Common mistakes

The most common mistake is a missing alt attribute. Without it, many screen readers read the file name instead, which sounds like “D S C zero zero four one dot J P G”. The second is stuffing keywords. Alt text is for people first; a clear description helps search too.

Text inside images is another trap. If a banner says “50% off winter coats”, the alt text must say the same words. Better still, use real text over the image so everyone can read and zoom it.

Alt text in popular tools

In WordPress, select the image and fill in Alternative Text in the block settings or the Media Library. In Shopify, open the image in the product page and choose Add alt text. In Wix and Squarespace, look for “What’s in the image?” or “Alt text” in the image settings.

Not sure which images are missing alt text? Accessible Nord lists every one, with the page and the code, so you can work through them in one sitting. Pair this guide with how to check colour contrast for two quick wins in one afternoon.

Sources

  1. The WebAIM Million, 2026 report
  2. W3C WAI: An alt decision tree
  3. Understanding WCAG 2.2: Non-text Content (1.1.1)

Last reviewed .

Frequently asked questions

How long should alt text be?

Usually one sentence, under about 125 characters. Some screen readers handle longer text, but short and clear is easier to listen to. Complex images like charts can have a short alt plus a longer description on the page.

Should every image have alt text?

Every image needs an alt attribute. Images that carry meaning get a description; purely decorative images get an empty alt (alt="") so screen readers skip them.

Does alt text help SEO?

Yes. Search engines and AI assistants use alt text to understand images and pages. Write for people first; clear descriptions naturally include the right words.

Can AI write my alt text?

AI can give you a first draft, but it does not know why the image is on your page. Always review it and adjust it to the context.

This guide is general information, not legal advice. For your specific obligations, check with a lawyer or your regulator.