To write alt text for SEO in 2026, work in this order: decide whether the image needs alt text at all, describe what it shows in the context of the page, name the specific subject, add a keyword only if it fits naturally, and leave the attribute empty for decorative images. Google Search Central calls alt text “the most important attribute” for giving Google metadata about an image, and the W3C Web Accessibility Initiative (WAI) supplies the decision tree that settles the first step. The need is real: WebAIM’s 2026 Million report, which scanned one million home pages from the Tranco ranking in February 2026, found 53.1% of home pages had images with missing alternative text.
Screen readers such as JAWS, NVDA and VoiceOver read alt text aloud, Google reads it alongside computer vision and the surrounding page, and the same sentence serves both audiences. This post covers the method, the examples, the failure patterns WebAIM measured, and what nobody has published a number for.
If you want the broader picture of image files, formats and delivery for AI answers, that is a separate topic covered in how to optimize images for AI search. This post stays on the alt attribute itself.
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What does Google actually say about alt text?
Google’s image guidance is short and specific. In its Google Search Central documentation on image best practices, Google says to write “useful, information-rich content” that fits the context of the page, and that it uses alt text together with computer vision and page content to understand what an image is about. It also says that if you link an image, the alt text works as the anchor text for that link.
Google gives a three step example in its own docs. A missing attribute is bad: <img src="puppy.jpg"/>. Keyword stuffing is also bad: an alt value that lists “puppy dog baby dog pup pups puppies” and food terms in one string. A one word alt of “puppy” is better, and alt="Dalmatian puppy playing fetch" is best. Google warns that filling alt attributes with keywords creates a bad user experience and may cause the site to be seen as spam, and it ties this to its spam policies.
Two limits are worth stating plainly. Google’s documentation gives no character limit or required length for alt text, so any “125 character rule” you read elsewhere is not a Google rule. And Google’s docs do not publish a measured ranking lift from rewriting alt text, so treat claims of a specific percentage gain as not tested by any primary source I can find.
Google also points to filenames and nearby text. It recommends short, descriptive filenames such as my-new-black-kitten.jpg over IMG00023.JPG, and it extracts subject information from captions, titles and the text near the image. Alt text works best as one of several signals that agree with each other.
What is the ordered method for writing alt text?
The method has five steps, and the order matters because the first step removes the most work. Each step maps to Google’s guidance or the W3C WAI decision tree, and the W3C tree is explicit that it does not cover every case, so use judgment on edge cases.
1. Decide if the image needs alt text at all
The W3C WAI decision tree asks whether the image is purely decorative or not meant for users. If so, use an empty attribute, alt="", so screen readers skip it. The same applies when the image repeats text that already sits next to it, such as a logo inside a link that also contains the company name as real text. Do not delete the attribute for these images. An empty alt and a missing alt are different, and WebAIM counts the missing one as a failure.
2. Identify the job the image does
The tree separates informative images (a photo or simple graphic that adds meaning), functional images (inside a link or button), images of text, and complex images such as charts. Each gets a different treatment. A search icon inside a button needs alt that says what the button does, not “magnifying glass.” W3C says to use the alt attribute to communicate the destination of the link or the action taken.
3. Describe the subject and the point, in context
For an informative image, W3C says to write a brief description that conveys its meaning. Ask what a reader who cannot see the image would miss on this page. “Dalmatian puppy playing fetch” works in Google’s example because it names the subject and the action. The same photo on a vet clinic’s “puppy vaccination schedule” page might need a different description, because context decides what matters.
4. Add a keyword only where it fits
If your target term is a natural part of an honest description, use it. If it is not, leave it out. Google’s warning about keyword stuffing is the one hard line here. A useful test is to read the alt text aloud as if it were a caption for someone who cannot see the page. If it sounds like a search query, rewrite it.
5. Handle charts and images of text separately
For a graph or other complex image, W3C says to include the information elsewhere on the page, in the body text or a table, and keep the alt short. For an image of text, such as a banner with a headline in it, put the same words in the alt unless that text already appears on the page. Google reads page text far more reliably than text baked into pixels, so prefer real text where you can.
What does bad versus good alt text look like?
Bad alt text falls into five patterns: missing, stuffed, redundant, filename-based and vague. Good alt text names the specific subject and, where it matters, the action or purpose. The table below uses the pattern from Google’s own puppy example and the W3C categories.
| Situation | Bad alt | Better alt | Why |
|---|---|---|---|
| Product photo | (attribute missing) | alt="Navy wool overcoat, front view" | A missing attribute gives no information to screen readers or Google |
| Blog hero photo | alt="coat winter coat buy coat cheap coat" | alt="Woman wearing a navy wool overcoat on a city street" | Keyword stuffing is called out in Google’s docs and spam policies |
| Image in a link | alt="button" | alt="Download the 2026 pricing guide (PDF)" | W3C: describe the destination or action |
| Team photo | alt="IMG_4471.jpg" | alt="The support team at the Denver office, 2026" | A filename tells nobody anything |
| Photo next to its caption | alt="Chef plating a dish in a restaurant kitchen" with caption repeating it | alt="" if the caption says the same thing | Redundant text adds noise for screen reader users |
| Chart | alt="chart" | alt="Bar chart: signups by month, full data in the table below" plus a data table | W3C: put the information elsewhere on the page |
| Decorative divider | alt="divider line" | alt="" | Decorative images should be skipped |
Our take: Spend your effort on the informative and functional images first. They are the ones where wording changes what a person, a screen reader or a search engine understands.
How common are alt text mistakes in 2026?
Very common, and the data comes from WebAIM, which runs the study itself. In the 2026 WebAIM Million report, 53.1% of home pages had at least one image with missing alternative text, and 16.2% of all home page images (an average of 10.8 per page) were missing it. That is down from 18.5% of images in 2025, so the trend is better, but the gap is still large.
Two more WebAIM findings matter for SEO work. First, 45% of the images missing alt text were linked images, and WebAIM notes that one out of every four linked images lacked alt text. Because Google treats the alt of a linked image as its anchor text, a missing alt on a linked image leaves a link with no descriptive label. Second, 10.8% of images that did have alt text used questionable or repetitive text, the kind WebAIM flags as things like generic words, filenames or text copied from nearby content.
So the realistic audit target is not “add alt everywhere.” It is: fix missing alt on linked images first, remove filename and generic values, and mark true decorations as empty. Missing alternative text ranked second among the six most common failure types WebAIM found in 2026, behind low contrast text on 83.9% of home pages.
What WebAIM does not tell you is whether fixing these raises rankings. It measures accessibility failures, not search results. The accessibility case is strong on its own, and the search case rests on Google’s statement that it uses alt text to understand images.
How do you roll this out across a whole site?
Start with templates, then the pages that matter most. A crawler such as Screaming Frog SEO Spider can export every image with its alt value, and WebAIM’s WAVE tool flags missing and suspicious alt on a single page. Both are named as plain tools, not endorsements.
1. Fix templates and linked images first
If a theme outputs alt="" for every featured image, fixing it once repairs hundreds of pages. Logos, icon buttons and image links come next, since WebAIM found a large share of its failures there. Give each one alt that states the destination or action.
2. Write alt by hand for your top images
Pick the images on your highest traffic and highest conversion pages and have someone who knows the page write each description. If you draft with an AI tool, review the output against the page.
3. Keep filename, caption and alt consistent
Google says it draws on captions and nearby text, so the image, filename, caption and alt should all point at the same subject. Re-run your crawl after any theme change, because alt text breaks quietly when a component is swapped.
Does alt text matter for AI search too?
Alt text helps because it is plain text attached to an image, and the systems that read your pages can use plain text. What is not established is how any given AI answer engine weighs it. No primary source from Google, OpenAI, Perplexity or Anthropic publishes a figure for alt text influence on citations, so any such claim is not tested in public data.
What you can say with a source: Google states that it uses alt text with computer vision and page context to understand images, and that it uses the alt of a linked image as anchor text. Treat that as the verified baseline. The related questions about file formats, sizes, captions and image placement for AI answers belong to the sibling guide on optimizing images for AI search.
A practical rule for 2026: write alt text for the person who cannot see the image. The rest follows, because Google’s documentation asks for the same thing, useful and specific description that fits the page.
FAQ
How long should alt text be?
Google’s image documentation gives no character limit or recommended length. The W3C WAI guidance says to write a brief description that conveys the meaning of the image. Aim for the shortest phrase that names the subject and, where relevant, the action or purpose, and move long explanations for charts into the page text. Treat any fixed number you read elsewhere as a house style, not a Google rule.
Should I put my target keyword in every alt attribute?
No. Google says to use keywords where they fit naturally and warns that filling alt attributes with keywords creates a poor user experience and may be treated as spam under its spam policies. If the keyword is an accurate part of the description, include it. If not, describe the image accurately and leave the keyword for the headline, body copy and title.
Do decorative images need alt text?
They need an empty alt attribute, alt="", not a missing one. The W3C WAI decision tree tells you to use an empty attribute for decorative images and for images that repeat nearby text, so screen readers skip them. WebAIM counts missing alternative text as a failure, which is why the attribute should stay present and empty rather than be removed.
Does Google use alt text for image search?
Yes. Google Search Central says it uses alt text along with computer vision algorithms and the contents of the page to understand the subject of an image, and that alt text is the most important attribute for providing metadata about it. Google does not publish how much weight alt text carries against other signals, so avoid treating it as a ranking lever on its own.
What is wrong with starting alt text with “image of”?
Screen readers already announce that an element is an image, so “image of” and “picture of” add words without adding information. Start with the subject itself. The one exception is when the type of image matters to meaning, such as “Bar chart” or “Screenshot,” because that tells the reader what kind of visual they are missing.
Can I use AI to write alt text for me?
You can use AI to draft descriptions, but review each one against the page. A model sees the pixels and not your intent, so it can describe a laptop on a desk when the point of the image is the dashboard on its screen. W3C says the right description depends on context, and a person who knows the page is best placed to judge that.
The short version
Alt text is a small job with a clear order. Decide if the image needs it, say what it shows in the context of the page, skip the keyword stuffing Google warns against, and mark decorations as empty. WebAIM’s 2026 data shows that over half of home pages still miss this, so doing it carefully puts you ahead of most of the web. If you want to see how your pages show up when people ask AI assistants about your category, check your site with our AI visibility audit.
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