Image SEO and alt text in the AI era
By Abhijay Tondak, Founder · Updated June 25, 2026 · 5 min read
Image SEO in the AI era still rests on text: descriptive alt attributes, meaningful filenames, and the surrounding copy tell search and AI engines what an image depicts. The biggest rule is to never trap facts inside an image - if a number, comparison, or step only appears in a graphic, an answer engine usually cannot extract it, so the text around the image must carry the meaning.
Key takeaways
- Alt text should describe what the image shows in plain, specific language.
- Never lock a citable fact inside an image - state it in the body text too.
- Use descriptive filenames and keep images compressed for crawl performance.
- Caption and surrounding text give engines the context an image alone can't.
- Decorative images get empty alt text so assistive tech and parsers skip them.
Engines read images through their text
While some engines apply vision models, you cannot rely on a machine to read a chart, infographic, or screenshot the way a person does. The dependable signal is text: the alt attribute, the filename, the caption, and the paragraphs around the image. Together these tell an engine what the image is and why it is there.
The practical consequence is a hard rule: do not let an image be the only place a fact lives. If your best statistic appears only in an infographic, it is effectively invisible to extraction. Put the number in the body text as a self-contained sentence, and let the image illustrate it rather than carry it.
How to write alt text that works
Good alt text describes the content and function of the image in plain language, specific enough that someone who cannot see it understands what it conveys. It is written for a human using a screen reader first - and that same description is what parsers use to understand the image.
- Describe what the image shows, not just that an image exists ('bar chart of X by year', not 'chart').
- Be specific but concise - a sentence, not a paragraph; no 'image of' preamble.
- Include the relevant entity or term naturally where it genuinely describes the image.
- For charts, summarize the takeaway in the alt and the exact numbers in the body.
- Use empty alt (alt="") for purely decorative images so they're skipped.
The technical basics still apply
Image SEO fundamentals haven't gone away. Descriptive, hyphenated filenames give a small but real signal. Compressed, appropriately sized files and modern formats keep pages fast, which protects crawlability and the user experience that AI traffic lands on. An image sitemap or proper markup helps discovery for image-heavy sites.
None of this replaces the core idea: the meaning has to be available as text. Treat every important image as a visual aid to a claim you have already stated in words, and you satisfy both the human reader and the engine trying to cite you.
Frequently asked questions
Do AI engines actually read alt text?
Alt text is part of the page's text content, so engines that parse the HTML can use it to understand an image and its context. It also drives accessibility and image search. It's the most reliable way to communicate what an image shows.
If an engine has vision, do I still need alt text?
Yes. Vision capability is uneven across engines and not guaranteed for any given crawl, and alt text remains essential for accessibility. Treat machine vision as a bonus, never as a substitute for describing the image in text.
What's the worst image SEO mistake for AI?
Putting a key fact only inside an image - a price, a comparison, a process diagram - with no text equivalent. The fact becomes unciteable. Always restate the substance of an infographic in the body copy.
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