Alt text is a short description of an image that shows if the image fails to load — but its real value goes much further. Search engines can’t “see” a picture the way people do, so alt text for images tells them what’s in it, while screen readers use it to describe visuals to people who can’t see them. Get it right and you improve accessibility and give your images a real shot at ranking.
What alt text is (and why it matters for accessibility and SEO)
Alt text — short for “alternative text” — is an HTML attribute that describes an image. It lives in the image tag, like <img src="chair.jpg" alt="Red leather office chair on castors">. If the image can’t load, the browser shows the alt text in its place.
For accessibility, it’s essential: people who use screen readers hear the alt text read aloud, so without it they simply miss whatever the image conveys. For SEO, search engines read alt text to understand what an image shows and whether it’s relevant to the page. That helps you appear in image search and reinforces what your page is about.
How search engines use alt text
Google and Bing index images separately from text. When they crawl a page, they read the alt attribute to catalog what each image depicts and how it relates to the surrounding content. Alt text is the bridge between a visual and the keywords a page targets.
If your alt text is descriptive and naturally relevant, the engine understands the image supports your topic. If it’s empty or says “image1,” the engine has to guess — and often guesses wrong. This matters most when your goal is to earn traffic from image results, a core part of image optimization for SEO.
How to write good alt text
- Describe what’s there, skip “image of.” The browser already knows it’s an image — just describe the content.
- Be specific but brief. Aim for about 5–12 words. Screen readers read every word, so don’t ramble.
- Work in a keyword only when it fits. If the page is about standing desks and the photo shows one, “white sit-stand desk with dual monitors” is perfect. Never force it.
- Don’t duplicate the caption. If a visible caption already says it, make the alt text add something rather than repeat it.
- Punctuate it like a sentence so screen readers pause naturally.
Alt text examples: good vs bad
- Bad: “graph” — Good: “Bar chart showing 2026 revenue growth by product category”
- Bad: “screenshot” — Good: “WordPress settings panel with caching and CDN options highlighted”
- Bad: “team” — Good: “Four teammates smiling in front of an office window”
- Bad: “IMG_7394.jpg” — Good: “Hexagonal white kitchen tiles being installed”
- Bad: “divider line” — Good: leave it empty (see below)
Common alt text mistakes to avoid
Keyword stuffing. “cheap coffee, organic coffee, fair-trade coffee beans” reads as spam and hurts the experience for screen-reader users. Keep it to one natural description.
Leaving everything empty. Skipping alt text entirely means engines can’t index your images and assistive tech has nothing to announce.
Dumping the file name in. “DSC_0421” tells nobody anything — replace it with a real description.
Over-describing. You rarely need every colour and object in the frame; capture what matters for the page.
When to leave alt text empty
Not every image needs a description. If an image is purely decorative — a border, texture, or spacer — use an empty attribute, alt="". That tells screen readers to skip it instead of announcing something pointless. The test is simple: if removing the image would lose meaning, write alt text; if the page still makes sense without it, leave it empty.
One last tip: heavy images slow the page down no matter how good the alt text is. Before uploading, run them through our free image compressor to keep file sizes small, and browse the rest of our free image tools for resizing and format conversion.
Frequently Asked Questions
How do I find and fix missing alt text on my site?
SEO plugins like Rank Math or Yoast flag images without alt text as issues. In WordPress, edit the post, click the image, and add alt text in the media panel. For large sites you can bulk-edit, but going through the editor is the safest approach.
Should alt text include a keyword every time?
Only when the keyword genuinely matches the image and the page topic. A relevant keyword helps; a forced one looks spammy and can do more harm than good. Describe the image accurately first, and let the keyword fit in naturally if it applies.
How long should alt text be?
Usually 5–12 words. Screen-reader users hear every word, so keep it tight. Complex images like detailed charts can run a little longer to capture the key data, but most photos and illustrations should stay short and clear.