What alt text actually does
How to write alt text that actually helps? Start with this test: read your alt text aloud to someone who can't see the image. If they can picture what's shown and understand why it's on the page, you wrote good alt text. If it sounds like a keyword salad or a filename, you didn't. Alt text serves two audiences at once — screen readers, which read it aloud to blind and low-vision users, and search engines, which use it to understand what an image contains. That dual job is why both accessibility and SEO guides converge on the same advice: describe the image honestly, and skip the tricks.
The fastest way to get this right is a three-word rule: describe, don't stuff. Before touching any tool, open your page's images and ask what each one contributes. A product photo exists to show the product. A chart exists to show the trend. A decorative divider exists to look pretty and contributes nothing. That judgment call — what is this image for — matters more than any SEO tactic, because alt text written to serve the reader almost always ends up serving search engines too. Google has said for years that its image understanding relies heavily on the surrounding context plus the alt text, and honest descriptions align with both.
Take a concrete before-and-after. A furniture store page shows a product photo. Before: alt text reads “sofa modern sofa grey modern living room sofa cheap sofas buy sofa online.” That's keyword stuffing dressed up as accessibility, and it reads horribly in a screen reader — imagine hearing that sentence spoken aloud. After: “Three-seat grey fabric sofa with oak legs, photographed at a slight angle against a white wall.” The second version tells a blind shopper exactly what the sighted shopper sees, and it still contains the words that matter — sofa, grey, fabric — placed the way a human would say them. One sentence does both jobs.
Before-and-after: charts and lifestyle photos
Now the same rule applied to a chart, where people go wrong differently. Before: “chart showing growth.” That tells a screen reader user almost nothing — growth of what, by how much? After: “Bar chart showing monthly blog traffic rising from 2,000 visits in January to 11,000 in June, with the steepest jump in April.” The trend and the numbers are the point of the chart, so they belong in the description. You don't need to recite every data point — capture the shape of the data and the headline numbers. If the full dataset matters, put it in a table or in the text next to the chart, and let the alt text summarize.
A third example, because lifestyle images are where the stuffing instinct runs wildest. A travel blog post shows a photo of a person kayaking at sunset. Before: “kayak adventure travel best kayak tours cheap kayak rental booking.” After: “Person in a red kayak paddling across calm water at sunset, mountains on the horizon.” The page is about kayaking in a specific place, so the surrounding text already carries the location and the tour details — the alt text only needs to describe what's visible. Resist the urge to repeat the page's keywords; the image's job is to show, not to rank on its own.
Some images should have empty alt text, and this surprises people. Decorative images — dividers, background flourishes, icons that repeat adjacent text — add nothing for a screen reader user, so the correct alt text is an empty string, which tells assistive technology to skip them. A page with twelve decorative flourishes that each announce “decorative line” is twelve interruptions for someone listening to the page. The W3C's guidance draws this line clearly: if an image is purely decorative, empty alt text is not laziness, it's courtesy. Spend your writing effort on the images that carry meaning.
When alt text should be empty
Here's the subtle skill that separates decent alt text from great alt text: context changes what you describe. The same photo of a laptop on a desk gets different alt text on different pages. On a laptop review: “Silver 14-inch laptop open on a desk, screen showing a spreadsheet.” On an article about standing desks: “Laptop on a desk raised to standing height next to a monitor.” The rule is to describe what's relevant to the page's purpose. Search engines reward this too, because context-matched descriptions reinforce what the page is about instead of dragging in unrelated words.
Length and format have practical rules worth memorizing. Aim for under about 125 characters — most screen readers handle that smoothly, and it forces you to be decisive. Never start with “image of” or “picture of”; the screen reader already announces that it's an image. End with a period so the reader pauses naturally before the next element. Skip special characters and emoji. And write in the page's language. These small formatting habits make your alt text sound like a person describing something rather than a machine filling a field.
The most common mistake is still keyword stuffing, and it's worth understanding why it backfires. Stuffed alt text reads terribly in screen readers — which is an accessibility failure first — and search engines have long treated obvious stuffing as a negative signal rather than a ranking boost. The second common mistake is leaving the filename as the alt text: “IMG_2026_final_v2.jpg” tells nobody anything and looks careless. The third is repeating the caption word for word; if the caption already says what the image shows, either trim one of them or give the alt text a different angle, like a detail the caption doesn't mention.
Let context choose the description
A fourth mistake deserves its own warning: describing the image while ignoring its function. A screenshot of a signup form with alt text “screenshot” is useless. “Signup form with email and password fields and a blue Create account button” tells a screen reader user what's actually there. Link images are a special case: if an image is inside a link, the alt text becomes the link's label, so it should say where the link goes — “Read the pricing guide” — not what the image depicts. Function first, appearance second, whenever the image does something.
Complex images need a different strategy than a single sentence can provide. A detailed infographic, a multi-series chart, or a technical diagram can't fit honestly into 125 characters. The accepted approach: give the alt text a concise summary — “Infographic comparing four email pricing plans by monthly cost and subscriber limit” — and put the full content in the page text nearby or in a linked long description. Accessibility guidelines have recommended this layered approach for years: a short label for navigation plus the complete information where everyone can reach it. Never cram a paragraph into alt text.
Now the workflow that makes good alt text actually happen instead of being a good intention. Images usually arrive on your site in two bad states: too heavy and poorly labeled. Fix both at once. First, run each image through FreeToolsBox's Image Compressor — smaller files mean faster pages, and page speed is an SEO factor that interacts with everything else you're doing. Second, while the image is in front of you, write the alt text using the describe-don't-stuff rule. Compress and describe in the same pass, image by image, before publishing. Ten images done this way beat a hundred “optimized later.”
The mistakes that still hurt
That same pass is also the moment to fix filenames. Rename “IMG_final2.jpg” to something descriptive like “grey-fabric-three-seat-sofa.jpg” before uploading, because filenames are another small signal search engines read. It takes five seconds during the compress-and-describe pass and saves you from a media library full of mysteries later. Pair the descriptive filename with the descriptive alt text, and you've covered the two text signals an image carries — one in the code, one in the markup — with honest, human writing instead of tricks.
For existing sites with hundreds of images, don't try to fix everything in a weekend. Sort your images by traffic: start with the pages that get the most visitors, then the pages you most want to rank. Fix the worst offenders first — the keyword-stuffed ones and the filenames-as-alt-text ones — because those are the ones that actively hurt. A spreadsheet with three columns (image, current alt text, new alt text) keeps the audit organized, and you can chip away at it fifteen minutes at a time. Steady progress on your top pages beats a heroic rewrite of your archive.
There's one more audience for alt text that's easy to forget: people on slow connections and anyone using text-only browsing. When images fail to load, browsers display the alt text in the image's place. Good alt text means a broken image still communicates; bad alt text means a broken rectangle with “banner_final_v3” under it. This is also why alt text matters for social sharing and RSS readers that strip images. Honest descriptions are resilient — they keep working in every degraded scenario.
Handling complex images
Social and CMS details are worth a quick pass. Most content management systems have an alt text field in the image uploader — that's where this lives, not in the caption field or the title attribute. The title attribute is not a substitute for alt text. If your CMS auto-generates alt text with AI, treat it as a rough draft and review every suggestion, because generated descriptions miss page context.
Measuring whether your alt text work pays off is simpler than most SEO measurement. In Google Search Console, the image search report shows which queries bring impressions to your images. For accessibility, navigate your page with a screen reader and listen to how the images sound in sequence — if the flow feels natural, you've succeeded; if you wince, you have your punch list.
A realistic maintenance habit keeps all of this from decaying. Make alt text part of your publishing checklist, right next to the headline and the meta description. When a writer uploads an image, the alt text gets written in the same sitting — not “later,” because later never comes. If you publish with a team, add one line to your style guide: “Alt text describes the image for someone who can't see it, in one sentence, no keyword stuffing.” That single sentence has prevented more bad alt text than any plugin.
The compress-and-describe workflow
Let's close with the mental model to carry forward. Alt text is a translation job: you're translating pixels into words for people who can't see the pixels, and search engines happen to read the same translation. Every technique in this guide — the describe-don't-stuff rule, empty alt for decoration, context-aware descriptions, the 125-character habit — follows from taking that translation job seriously. Do that, keep your images fast with FreeToolsBox's Image Compressor (our full walkthrough: compressing images without looking cheap), and your images will serve every visitor and every crawler the way they're supposed to.
One last check before you publish: read each alt text aloud and ask whether a blind listener would understand the image and its purpose, then delete any phrase that exists only for search engines. If the sentence survives that test, it's good alt text — the SEO benefit follows automatically, because the clearest description is exactly what both humans and algorithms want.