Writing Alt Text for Accessibility and SEO
Describe what is in your image, optionally add the page topic for context, and this tool writes four alt text options — each concise, descriptive, and written to describe the image rather than to stuff keywords into it.
Alt text is the text alternative for an image. Screen readers announce it to people who cannot see the image, browsers display it when an image fails to load, and search engines use it to understand what the image shows. It is one of the few pieces of markup that serves accessibility and SEO with exactly the same solution.
What good alt text looks like
Good alt text describes the image the way you would describe it to someone on the phone who needs to know what it shows. “Blue and white running shoe on a rubber track” tells them something. “running shoes buy running shoes best running shoes” tells them nothing and actively degrades the experience for a screen reader user.
Length should be enough to convey the content and no more — roughly 125 characters is a common working guideline, since some older screen readers truncate around there. If an image genuinely needs a paragraph to explain, that explanation belongs in the page text where everyone benefits from it.
Do not begin with “image of” or “picture of”. Screen readers already announce that an image is present, so the prefix is redundant and wastes the listener's time on every single image.
Decorative images and empty alt
Not every image needs describing. Purely decorative images — background flourishes, spacer graphics, an icon sitting next to text that already says the same thing — should carry an empty alt attribute, written as alt="".
An empty alt is a deliberate instruction telling screen readers to skip the image entirely. This is completely different from omitting the attribute, which leaves the reader to guess: many screen readers respond by announcing the filename, so a user hears “I M G underscore 4 7 2 dot J P G” read aloud.
The test is straightforward: if removing the image would lose information the reader needs, describe it. If removing it would change nothing but the aesthetics, use an empty alt.
Alt text and image SEO
Alt text is the primary way search engines understand image content, which makes it the main lever for ranking in image search. For some sites — recipes, products, travel, anything visual — image search drives a meaningful share of total traffic.
It also contributes to the page's overall topical signals, though only modestly. The mistake is treating that as licence to keyword-stuff. Google's own image guidelines explicitly call out keyword stuffing in alt attributes as spam, and it makes the page worse for the users the attribute exists to serve.
Filenames matter too, and they are easier to get right. running-shoe-track.jpg communicates something; IMG_4721.jpg does not. The URL Slug Generator is a quick way to turn a description into a clean hyphenated filename.
Context changes the right answer
The same image can need completely different alt text depending on why it is on the page. A photo of a running shoe on a product page might be “Nike Pegasus 41 in blue, side view”. The same photo illustrating an article about pronation might be “Running shoe showing worn outer edge from overpronation”.
This is why the tool asks for the page topic as well as the image description. The relevant detail is whatever the surrounding content is about — describe the aspect of the image that matters here, not every visible attribute.
Images that are also links need particular care. If an image is wrapped in an anchor and has empty alt text, the link has nothing describing where it goes, which is both an accessibility failure and a wasted internal link. The Internal Link Analyzer flags links with no usable anchor text, including image links.
Auditing existing images
Most sites accumulate missing alt text over years, usually because a CMS makes the field optional and nobody enforces it. The On-Page SEO Analyzer reports how many images on a URL are missing meaningful alt text, which gives you a per-page number to work from.
Prioritise by page value rather than trying to fix everything at once. Images on your highest-traffic pages, product images, and images inside content that ranks are worth doing first. Decorative theme graphics can wait, and often just need an empty alt applied in the template.
- Informative images — describe what they show, in context.
- Decorative images — empty alt (alt=""), never a missing attribute.
- Functional images such as icon buttons — describe the action, not the icon.
- Images of text — repeat the text exactly, or better, use real text instead of an image.
- Charts and complex graphics — give a short alt and put the full explanation in the page text.
Frequently asked questions
How long should alt text be?
Long enough to convey what the image shows, and generally under about 125 characters. Some screen readers truncate around that point. If an image needs more explanation than that, put the detail in the page text where every reader benefits.
Should I include keywords in alt text?
Only where they occur naturally in an accurate description. If the image genuinely shows running shoes, saying so is both accurate and keyword-relevant. Adding keywords the image does not depict is stuffing, which Google's image guidelines treat as spam.
What is the difference between empty alt and no alt?
Empty alt (alt="") deliberately tells screen readers to skip a decorative image. A missing alt attribute leaves them guessing, and many respond by reading the filename aloud. Decorative images should always have empty alt rather than none.
Does alt text help with rankings?
It is the main signal for image search rankings and contributes modestly to the page's topical relevance. Its clearest benefit, though, is accessibility — and in many jurisdictions that is a legal requirement rather than an optimisation.
Can AI write alt text without seeing the image?
It writes from the description you provide, so the output is only as accurate as your input. Always check the result actually matches the image before publishing — inaccurate alt text is worse than none for someone relying on it.