Image Alt Text for SEO: 2026 Writing Guide
One product page can hold three images that each need different alt text. A photo of the product needs a short description, and a thin divider between sections needs an empty alt attribute. A small cart icon that is the only content of a link needs the action itself: Add to cart.
Our take: alt text is a job description for the image, not a caption and not a keyword slot. Ask what the image does on this page, then write that. Most bad alt text comes from describing the picture when the image is really a button, or describing it at all when it is decoration.
This guide helps content and store teams, bloggers, developers, and anyone whose checker keeps flagging missing image text.
What does alt text do for people and for Google?
The alt attribute gives a text version of an image to people who cannot see it, including screen reader users and people on slow connections. Google calls it the most important attribute for image metadata, and reads it with computer vision and the page around it to understand what the image shows.
Google Search Central makes this point on its Image SEO best practices page, last updated March 2, 2026: "Google uses alt text along with computer vision algorithms and the contents of the page to understand the subject matter of the image." For people, WCAG 2.2 Success Criterion 1.1.1 asks at Level A for a text alternative "that serves the equivalent purpose". Visual search is a separate topic, covered in our visual search guide.
How do you decide what an image needs?
Use the W3C alt decision tree from the Web Accessibility Initiative, which asks, in order, whether the image contains text, sits in a link or button, adds meaning, or is pure decoration. The first answer that fits tells you to write the words, name the action, describe the meaning, or leave the alt empty.
Here is the WAI alt decision tree in plain words.
- Text in the image: if the same words sit nearby as real text, use an empty alt, and if they appear nowhere else, put them in the alt.
- A link or button that makes no sense without the image: name where it goes or what it does.
- An image that adds meaning: a simple photo gets a brief description, a graph gets its information written out on the page, and a repeat of nearby text gets an empty alt.
- Pure decoration: an empty alt.
- Anything else: the tree itself says, "This decision tree does not cover all cases."
My view: the tree works because it asks what the image does here, not what it shows.
How should you describe a photo that carries meaning?
Our take: name the specific thing a sighted reader gets from the photo on this page, in one short phrase or sentence. Google's own examples run from bad to best: no alt at all, a pile of keywords, a single word, and then a specific phrase such as "Dalmatian puppy playing fetch".
For example, a Denver, Colorado bike shop uses one photo of a green touring bike on a product page and in a buying guide: the product page alt might read green steel touring bike with front and rear racks, and the guide might use touring bike packed with bags on a gravel road. Our guide to fixing product pages that fail covers the rest of that page, from product copy to variants.
What should an image link, logo or icon say?
Say what the link or button does, not what the picture shows: for an image link, Google uses the alt as anchor text. W3C gives the same advice for people: a printer icon should say print this page, a magnifier should say search, and a linked logo should name the site plus home.
Google's Link best practices page, last updated December 10, 2025, says: "For images as links, Google uses the alt attribute of the img element as anchor text". W3C Functional Images adds that screen readers will typically read out a file name or URL when such an image has a missing or empty alt, but a logo beside the same words inside the link takes an empty alt, which avoids saying the name twice. Our internal linking guide covers anchor text more widely.
When should the alt attribute be empty?
Leave the alt empty when the image adds no information to the page: borders and spacers, an icon that only dresses up link text, pure eye candy, or a photo the nearby text already names and describes. Keep the attribute itself: an empty alt lets screen readers ignore the image.
The W3C Decorative Images page explains why the attribute must stay: "Leaving out the alt attribute is also not an option because when it is not provided, some screen readers will announce the file name of the image instead." It adds that "Whether to treat an image as decorative or informative is a judgment that only the author can make". W3C also suggests CSS backgrounds for decoration where possible, and Google notes that "Google doesn't index CSS images."
How do you handle images of text, charts and diagrams?
If an image shows words that appear nowhere else on the page, put those words in the alt. A chart or diagram needs two parts: a short alt that names it and points to the details, and a longer description in the page text that everyone can read, search engines included.
The chart method comes from the W3C Complex Images tutorial: a plain text link to the long description works in all browsers and assistive technologies, and W3C says the description is then available "to everyone, including search engines and other programs." Our take: if a chart matters, its numbers belong in the page text or a table anyway. Video has its own text alternative in captions and transcripts, covered in our video SEO guide.
What are good alt text examples for each image type?
The table below maps seven common image types to what the alt should say, based on the W3C tutorials and Google's image page. The last column is our own plain example, and where it says empty alt, keep the attribute and leave its value blank. Use it as a quick check while you edit.
The second and third columns paraphrase Google and W3C pages, saved on October 7, 2026. The fourth is our own example.
| Image | What the alt should say | Source | Our example |
|---|---|---|---|
| Product or editorial photo | A specific phrase for what it shows on this page | Google Image SEO best practices | red wool scarf on a pine table |
| Logo alone in a home link | The destination, site name plus home | W3C Functional Images | Bike shop home |
| Icon button, such as print or search | The action, not the icon | W3C Functional Images | Search the store |
| Image of text | The words the image shows | W3C alt Decision Tree | Free returns on all orders |
| Chart or diagram | A short name, with full detail in the page text | W3C Complex Images | Map of delivery zones, described below |
| Decorative border or background | Nothing, and use CSS where possible | W3C Decorative Images | empty alt |
| Photo already described by its caption | Nothing, the caption covers it | W3C Decorative Images | empty alt |
How long should alt text be?
Our take: as long as the job needs, which is usually one short sentence or less. Google's image page and the W3C pages behind this post set no character limit, and in our view, the short limits quoted around the web are habits, not rules. For a chart, keep the alt short and put the detail in the page.
My view: write until a listener has what a sighted reader got, then stop.
How is the alt different from a caption, a filename and a title?
Our take: the alt replaces the image for someone who cannot see it, while a caption sits on the page for everyone. Google says it reads page content "including captions and image titles", and that filenames give only "very light clues". Each field has its own job, and copying one into another wastes it.
Google also asks you to place images near relevant text. In our view, that is a reason to write good captions, not to copy them into the alt. Our image optimization guide covers filenames, formats and compression, and our Open Graph tags guide covers the separate image used for social sharing.
Should keywords go in the alt attribute?
Our take: only when the keyword is the true name of what the image shows, and then once. Google asks for useful content that uses keywords appropriately and fits the page. It warns against filling alt attributes with keywords, "as it results in a negative user experience and may cause your site to be seen as spam."
If a photo shows a blue enamel camping mug, those words belong in the alt text once. Our keyword density guide covers how Google's spam policies treat stuffing. My view: read the alt aloud, and if it sounds like a search box, cut it back.
How do you handle the alt at scale and in other languages?
Our take: build templates from real product data, such as color, material and model, and never use one string for every image. Treat any generated description as a draft that a person checks, because only the author knows why an image is on the page. Translate the alt with the page, and the filenames too.
Our guide to programmatic pages built from one template applies this to whole pages. For example, a Lyon, France bakery runs its menu page in French and English: each version carries alt in its own language, and the filenames are translated too, which Google's image page advises for localized images. The tags that pair the French and English pages are a separate job, and our hreflang guide covers them. In South Korea, for example, a Busan cosmetics brand page in Korean needs alt in Korean, and our take is that a native speaker should write it. If Naver matters to you too, our Naver guide covers that side.
How do you audit alt text across a whole site?
Our method: list every image on the site and sort each one into missing alt, empty alt, or filled alt. Check that every empty one is truly decorative, that every image link has words, and that filled ones are not keyword lists or leftover file names, and then fix the worst group first.
Start by crawling the site to list every image with its page URL and alt value, and for a first pass, try Deque's axe rule, Images must have alternate text, which rates a missing alt as Critical for user impact. Deque maps it to WCAG 2.0, 2.1 and 2.2 at Level A, Section 508, Trusted Tester and EN 301 549. If images arrive by script, check the rendered page, as our JavaScript rendering guide explains.
Our technical SEO audit guide shows how to prioritize fixes, and our web accessibility and SEO guide covers the law in the United States and Europe, including the European Accessibility Act. For the rest of the page, see our SEO checklist for individual pages and our heading tags guide.
Where to start: fix every image link that has no words first. Next, give pure decoration an empty alt, and then rewrite the alt on the images of your top product and landing pages. Last, set a template rule for new uploads, and make the alt a required field before any page goes live.
Frequently asked questions
Should every image have an alt attribute?
Yes, every image element should carry the attribute, even when its value is empty: the W3C Decorative Images page explains that leaving it out is not an option, because some screen readers will then announce the file name instead. Deque's axe rule rates a missing alt as Critical for user impact. Informative images get words, image links get their destination or action, and decoration gets an empty value. Our take: a missing attribute is a bug, and an empty one is a choice.
Is an empty alt the same as no alt at all?
No, and the difference matters: an empty alt is a clear signal that the image can be ignored, and W3C says decorative images should get a null alt for that reason. A missing attribute sends no signal, and the W3C Decorative Images page warns that some screen readers will then announce the file name. For an image link, Google's link guide counts an empty alt with no link text as a bad example, which leaves the link with no words.
Should the alt start with "image of"?
Usually not, and Deque's notes for the axe rule say words such as chart, image and diagram tend not to be useful in the alt. The W3C Functional Images page makes a related point for buttons: write print this page, not image of a printer. Our take: spend the words on what the image means. One exception is when the medium matters, such as a painting shown beside a photo of the same scene, and then the word painting tells the listener something real.
What about background images set in CSS?
Pure decoration belongs there, and only pure decoration: the W3C Decorative Images page says decorative images should be CSS backgrounds where possible. Google's image page adds that "Google doesn't index CSS images." That is fine for a texture, a divider or a spacer, but the WCAG 1.1.1 page lists putting information only in CSS background images as a failure. Our take: any image a person would miss, and any image you want in Google Images, needs a real image element with a fitting alt.
How do I label an SVG drawn in the page?
An SVG drawn in the page works differently from a normal image file: Google's image page says the alt attribute is for the HTML image element, while inline SVG can use the title element. The words follow the same rules: say what the graphic means or does on this page. For an icon in a button, name the action, as W3C Functional Images advises. For pure decoration, the WCAG 1.1.1 page asks that it be built in a way assistive technology can ignore.
What should the alt say for a CAPTCHA?
Describe its purpose: the WCAG 1.1.1 page treats CAPTCHA as a special case, because a text copy of the puzzle would let robots solve it. Its answer is a text alternative that names what the CAPTCHA is for, such as a check that the visitor is a person, plus a second form of the test that uses a different sense. Our take: ask whether the form needs a CAPTCHA at all, as the same page notes that every type shuts out some users with disabilities.
Should the alt repeat the caption?
No. When the caption already names and describes the photo, the W3C Decorative Images page lists that as a case for an empty alt, and the same page says text on such images adds audible clutter for screen reader users. Our take: use the alt only for something the caption leaves out that a sighted reader would notice, such as the setting, and keep it short. When the caption covers it all, leave the alt empty and let the caption do the work.
Should the alt change when one image sits on two pages?
Often, yes, because Google asks for alt that is "in context of the content of the page". The examples on the WCAG 1.1.1 page show one picture of the world used as a link on a travel site and on a university site, with different text on each. Our take: the file can stay the same while its alt follows the job it does on each page. Google's image page also suggests using the same image URL each time, which lets Google cache and reuse it.
Do images in an image sitemap still need alt text on the page?
Yes: Google's image page describes an image sitemap as a way to tell Google about images it might not otherwise discover. The alt still lives on the page, inside the image element, where Google reads it with the page text and where screen reader users meet it. Our take: the sitemap aids discovery and the alt describes the image, and you need both. A sitemap entry with no alt on the page leaves people who cannot see the image with nothing.
Can the alt include a brand name?
Yes, when the brand is part of what the image shows. A photo of a branded jacket on its product page can name the brand, the item and the color. Google asks that keywords be used appropriately and in context, and a true brand name fits that, but adding the brand to every divider and icon does not. Our take: if the logo alone links to your home page, the brand name belongs in the alt with the word home, as W3C advises.