How long should alt text be?

Alt text is the text in an image's alt attribute. A screen reader reads it aloud in place of the image, and a browser shows it when the image does not load, as WebAIM's alternative text article explains. Its length follows from what the image does on the page, which is why WCAG and the HTML Standard name no number. WCAG success criterion 1.1.1 Non-text Content (Level A) asks for a text alternative that serves the equivalent purpose. For most images that purpose fits in a few words, some need a sentence, and a chart or diagram needs a short alt attribute plus a longer description in the page.

This page is about how much to write. For what to write, start with our complete guide to alt text and the alt text examples.

What the standards say about alt text length

Four sources shape the answer. None sets a character count. All four tie the alt text to what the image does on the page, and W3C and WebAIM add that anything longer belongs in the page text.

Google's image SEO best practices (the page shows an update date of March 2, 2026) ask for useful, information-rich alt text in the context of the page. They give no length either, and their best example is a short phrase.

The sources differ in emphasis. The HTML Standard's examples run from one word on a topic icon to several sentences for a screenshot in a gallery, where the image is the point of the page. W3C and WebAIM steer long content out of the attribute. We follow the stricter guidance because it serves more listeners. That is our reading, not a rule.

Is there a character limit for alt text?

No. None of the sources above names one. The figure you will see repeated is 125 characters.

Accessibility specialist Eric Eggert, who says he helped write W3C's images tutorial, called the idea that screen readers cut alt text off at that point a myth in a February 2022 post. He reports that a test by Terrill Thompson found no screen reader cutting the text off altogether, and that JAWS splits long alt text into shorter pieces, which, he guesses, people mistook for truncation. That is one practitioner's report, and the test page it links returned a page-not-found error when we tried it in October 2026. Treat it as a reason to doubt the myth, not proof of how every screen reader behaves.

A number can still work as a prompt. Our free alt text generator aims for under 125 characters, in one sentence, where possible. That is our own target for a draft, not a standard. If a description runs well past it, ask whether it has drifted into detail the image's purpose does not need.

Why shorter alt text usually works better

The limit that matters is the listener's. In an April 2024 post that he updated that November, Adrian Roselli tested a deliberately long alt text in several browsers and screen readers. He writes that the limit is not on what is allowed but on what people can use. Three reasons to keep alt text short come from his tests and the standards.

• It has no structure. Alt text is plain text, so a listener cannot move through it by word or paragraph. In Roselli's tests NVDA split the long text into chunks and announced each one as a graphic, while JAWS with Chrome and VoiceOver gave no way to step backward through it, so a missed detail can mean starting over.
• It stands in when the image does not load. In Roselli's tests, Chrome clipped it to the space set for the image, and Safari showed none of it when it was longer than the placeholder.
• It competes with the page. The HTML Standard says alt text should not repeat information in the prose next to the image and should not hold the image's caption. Our guide to captions versus alt text covers the split.

Roselli adds that social media is no excuse to ignore this advice. See alt text on social media.

Too short is a failure too

Length is not the measure of quality in either direction. Alt text that is short and empty of information fails the same purpose as alt text that is long and padded. Typical short failures are a placeholder such as "image" or a file name, which tells the listener nothing (our free scan flags these), and a label in place of a replacement. The HTML Standard says "sales graph" would be inadequate alt text for a sales graph, because alt text has to carry the image's message, not name it. Google's own example ladder also ranks a bare "puppy" below a specific description.

Very short text is exactly right in some cases. WebAIM's example is a PDF icon beside the link text "Download the employment application": the best alt text is "PDF". A purely decorative image should have an empty alt attribute, covered in our decorative images guide.

How much to write for each kind of image

Use this table as a starting point, then adjust for what the text around the image already says. The examples are invented.

The icon, logo and image-of-text rows follow the HTML Standard's sections on icons and logos and text rendered to a graphic. For product photos, see alt text for product images.

When one sentence is not enough: a short alt plus a long description

W3C's complex images tutorial covers images that hold more than a short phrase or sentence can carry: graphs and charts, diagrams the page text relies on, and maps. They need a two-part text alternative. The short description identifies the image and, where it helps, says where the long description is. The long description gives the essential information as text, including values, relationships and trends.

W3C advises making the long description available to everyone, for example as part of the main content, and summarizing the image in the surrounding text. Its approaches are a link next to the image (alone or inside a figcaption), the long description's location named in the alt attribute, a figure whose figcaption holds the whole description, and aria-describedby pointing to a paragraph. That last one suits only text-only descriptions, because assistive technology reads the referenced element as one continuous paragraph and drops headings and tables.

Naming the location in the alt attribute looks like this:

<img src="orders.png"
     alt="Line chart of monthly orders. Full figures are under the heading Orders by month.">
...
<h3>Orders by month</h3>
<table>...</table>

If a chart's whole message fits in one sentence, that sentence can be the alt text, as in one of the HTML Standard's graph examples. If it is a table's worth of data, it cannot. WebAIM notes that the longdesc attribute is deprecated and should not be used. Our chart alt text guide has worked examples.

What to cut when alt text runs long

If a draft feels long, cut in this order:

1. Words that announce the medium. W3C says "image", "icon" and "picture" are usually unnecessary because screen readers announce the image. Keep the medium only when it matters, such as a painting versus a photograph.
2. Words that repeat the caption or nearby text. The HTML Standard says never to put the caption in the alt attribute.
3. Detail the image's purpose here does not need.
4. Keywords, slogans, credits and web addresses. Google warns that keyword stuffing gives a poor experience and may get a site seen as spam, and Roselli lists credits and URLs among the things to leave out. See alt text and SEO.
5. Data and long explanations. Move them into the page and point to them.

Whatever stays, W3C advises putting the most important information first.

One image at three lengths

Take a photo of a yellow rain jacket worn on a hill trail, on a store's product page where the heading and price already name the product. The jacket is an invented example.

Check it yourself

Three checks take a few minutes on any page:

1. Read it aloud. W3C and the HTML Standard both suggest imagining you are reading the page aloud over the phone to someone. If you stumble, cut words.
2. Swap each image for its alt text. By the HTML Standard's rule, the meaning of the page should not change. A sentence you can remove without loss is excess. If the page now makes less sense, something is missing.
3. Read the longest alt attributes first. They are the likeliest to be carrying data, captions or keywords.

Then run the tools. The free alt text checker downloads up to six images from a page and judges whether each alt text is true of its image. It flags wrong, vague and filename alt text, and decorative images that are being read out. The alt text generator writes a draft for an image you upload, which you then edit. Scan my site for free flags images with no alt attribute and alt text that is a placeholder, such as a file name or the word "image", on the pages it scans.

The checker and the scan do not grade length. A check that reads only the HTML can flag unusually short or long alt text, but it never opens the image, so it cannot tell you whether short alt text is true. Our AI alt text accuracy test shows why that gap matters.

Keep it checked

A one-off review covers the images as they are on the day you look. GotAlt checks the pages you monitor every week. It compares the alt text of up to six images per page with the image itself, runs its rule checks, opens monitored pages in a browser for contrast and other checks that need a rendered page (see what we check), and reports what changed. Plans are from $69 a month. Audit my whole site from $69/mo.