Alt text is the quietest part of your website and one of the most underrated. It decides whether screen readers can describe your images to blind visitors, whether Google can rank your photos in image search, and whether your product pages survive an accessibility audit. Yet most sites either skip it entirely or fill it with junk like "IMG_0421" and "image1". AI vision models changed the equation: they can describe any image in seconds. The trick is using them without letting them flatten every description into the same bland, generic sentence.
Why alt text actually matters
Alt text serves three audiences at once, and AI helps with all of them.
First, accessibility. Screen readers read the alt attribute aloud when a user encounters an image. If it is missing, the user hears a filename or nothing at all. In the EU, the European Accessibility Act has pushed alt text from a nice-to-have into a compliance requirement for many commercial sites, and the ADA in the US has driven plenty of lawsuits over inaccessible image-heavy pages. Good alt text is not a legal hack, though. It is simply how you include millions of people in your content.
Second, SEO. Google cannot see images the way humans do. It reads your alt text, your captions, and the surrounding content to decide what an image shows and whether it belongs in image search results. Descriptive, natural alt text with a relevant keyword is a genuine ranking signal for image SEO. Keyword-stuffed alt text ("cheap shoes buy shoes best shoes shoes") is a spam signal, which is exactly the kind of output you must edit out of AI drafts.
Third, resilience. When an image fails to load, the browser shows the alt text in its place. A page full of broken-image icons with filenames looks abandoned; the same page with descriptive alt text still communicates.
What good alt text looks like (the rules AI doesn't know)
Before handing anything to an AI tool, learn the rules so you can judge its output. Most guides agree on these:
Keep it under 125 characters. Many screen readers cut off alt text around that point. One concise sentence is the target, not a paragraph.
Don't say "image of" or "picture of". Screen readers already announce "graphic" or "image" before reading the alt text. Starting with "image of a dog" makes a blind user hear "image: image of a dog".
Describe what's in the frame, guided by context. The same photo needs different alt text on a photography blog ("golden hour over mountain peaks, low clouds in the valley") versus a hiking shop ("two hikers with red backpacks crossing a mountain pass at sunset"). Context decides which details matter.
Decorative images get empty alt text. If an image exists purely for decoration — dividers, background flourishes, stock-photo texture — the correct alt text is alt="", which tells screen readers to skip it. Describing every decoration clutters the listening experience.
Never stuff keywords. Use the page's target keyword only when it describes the image naturally. One keyword, maximum, and only if it fits.
The AI workflow: generate, then edit
The workflow that actually works is two steps, and skipping the second one is where most people go wrong.
Step 1: Generate a first draft with an AI vision model
Upload the image (or point the tool at your media library) and let the model describe it. This is the part AI is genuinely good at: identifying objects, scenes, colors, and composition quickly. For a single image, this takes seconds. For a media library of 500 images, this is the difference between an afternoon and never.
Step 2: Edit every draft before it goes live
AI alt text has predictable failure modes. It hallucinates details that aren't there ("smiling woman" when nobody is smiling), misses brand and product names entirely, writes the same flat sentence structure for everything, and has no idea what the image means on YOUR page. A thirty-second edit per image fixes all of this: correct errors, swap in the right product name, and add the keyword where it fits naturally.
Think of it as AI doing the typing and you doing the thinking.
Real AI tools for generating alt text
These are real, working tools — use the free options to start.
Onylogy Image Alt Text — a free, open-source WordPress plugin that generates alt text (plus optional captions, titles, and descriptions) for your whole media library using vision models. You bring your own API key — Groq is the default, and it also supports Google Gemini, OpenRouter, Mistral, and others, most of which have generous free tiers. It writes into WordPress's native alt fields, so the results work with every theme, SEO plugin, and screen reader, and it stays in place even if you remove the plugin. It has a review mode where you approve or edit each suggestion, which is exactly the workflow recommended above. Bulk generation across hundreds of images with a progress bar makes it the strongest free option for WordPress users.
AltText.ai — a dedicated alt text generator that works on WordPress, WooCommerce, and Shopify. It combines image recognition with your product data so descriptions include real product names instead of "a blue shirt". The first 25 images are free, with plans starting around $5 per month. Best for store owners who need product-aware descriptions at scale.
ImageSEOAI — a Chrome extension that generates SEO-friendly alt text directly in your browser as you work. Handy for teams that manage images across multiple platforms rather than one CMS.
Alt Text Creator — a browser extension that uses OpenAI's GPT-4 with Vision to generate alt text for images on any page. Useful when you're editing pages in a custom CMS or a website builder without plugin support.
Altnado and Describe Image — free web-based generators where you upload an image and get a description back. Fine for occasional one-off images, blog posts, or social media graphics when you don't want to install anything.
The pattern is clear: if you live in WordPress, a plugin like Onylogy handles the bulk work; if you manage images elsewhere, a browser extension or web tool covers the gaps.
How to edit AI alt text like an SEO editor
Keep a mental checklist and run every AI draft through it:
1. Fix hallucinations. AI models sometimes invent text, people, or objects. Compare the description against the actual image. This is the highest-value thirty seconds you can spend.
2. Add the proper noun. AI writes "a person holding a microphone"; you write "podcast host Maya Chen holding her Shure SM7B microphone". Product names, people, places, and brands are what make alt text useful and rankable.
3. Match the page context. If the image sits on a page about trail running shoes, the alt text should say what the shoes look like and that they're being used on a trail — not describe the background mountains at length.
4. Cut the filler. Remove "image of", "photo showing", and any sentence AI padded to sound complete. Alt text is a caption, not an essay.
5. Add one keyword naturally — or none. If your page targets "trail running shoes" and the image shows them, use it. If it doesn't fit, skip it. Forced keywords read badly to screen readers and to Google.
Example of the difference this makes. AI output: "A person running on a trail in the forest wearing shoes." Edited: "Runner mid-stride on a forest trail wearing lightweight trail running shoes with red laces." Same facts, but now it names the subject, fits the page, and carries the keyword without sounding stuffed.
Bulk workflow for existing media libraries
If your site already has hundreds of images with missing alt text, work backwards instead of one post at a time:
- Install a bulk generator (Onylogy on WordPress) and run it across your media library in review mode.
- Start with the highest-traffic pages: product images, featured images on popular posts, and images that rank (or should rank) in image search.
- Batch your edits by image type. Product photos all need the product name; blog featured images need the article's keyword; staff photos need the person's name and role. Reviewing twenty product photos in a row is faster than mixing types.
- Leave decorative images alone — set their alt to empty and move on. Not every image needs a description; that's what the null alt attribute is for.
Common mistakes to avoid
Publishing AI output untouched. Unedited AI alt text is better than no alt text, but only barely — it hallucinates, misses proper nouns, and sounds robotic across a whole site.
Writing novels. Alt text over 125 characters gets truncated by screen readers. If the image genuinely needs a long description (a chart, an infographic), put the details in the surrounding text or a linked long description, and keep the alt text itself to a summary.
Using filenames as alt text. "DSC_4521-final-2.jpg" tells a screen reader user nothing and tells Google nothing. It is the most common failure on older sites.
Duplicating the caption. If the image already has a visible caption, the alt text shouldn't repeat it word for word — screen reader users hear both, back to back. Make the alt text complementary.
Skipping alt text on linked images. If an image is a link (a product thumbnail, a logo), its alt text doubles as the link's label. "Nike Air Zoom Pegasus 40" on a product thumbnail tells a screen reader where the link goes; "shoe photo" does not.