First, Do the Arithmetic
Alt text is a Level A requirement in WCAG — the baseline conformance level, not an advanced one. Success criterion 1.1.1 Non-text Content states that all non-text content presented to the user must have "a text alternative that serves the equivalent purpose." Miss it and you fail the lowest bar in the standard, which is why the pressure has grown on anyone running an image-heavy WordPress site.
The plugins that fix this in bulk all advertise a free tier, and the free tier is almost always metered per month. That makes the important number not the cap itself but the cap against your library size. Count your images first — the WordPress Media Library shows the total — then divide:
- A 300-image blog — any free tier clears it in weeks. Pick on quality, not quantity.
- A 2,000-image site — 50 a month is over three years; 15 a month is more than eleven. The free tier is not a plan, it is a sample.
- A 10,000-image WooCommerce store — no monthly free tier will ever catch up. Go straight to the backlog routes below.
The Free Plugins, With Their Real Caps
AI Alt Text Generator Best free plugin
Its wordpress.org listing states that every site gets 50 free images per month through a managed service, and that it works out of the box — no API key and no signup required. It bulk-generates across the whole library or runs automatically on upload. With 2,000+ active installs and an update three weeks before this was written, it is also the best-maintained of the genuinely free options.
Fifty a month is the sweet spot for an active blog: it covers new uploads comfortably and chips away at the backlog.
Unleash AI 200/month, but check the date
On paper the most generous free tier in this comparison: a "Forever Free Plan" with 200 credits per month, where one credit equals one title, description or alt text generation — so 200 alt texts, or fewer if you also generate meta titles. It bulk-updates pages and images at once.
The caveat is not about the allowance. Its listing shows the plugin was last updated around two years ago, that it has not been tested with the last three major WordPress releases, and that it has roughly 20 active installs. An unmaintained plugin with write access to your media library is a real risk, not a theoretical one. If you install it, test on staging and check compatibility yourself.
AltTextLab 25/month, 130+ languages
A permanent free plan of 25 credits per month with no credit card. Its Bulk Generate feature scans the entire existing media library and processes every image with missing alt text in one run, and it generates in over 130 languages with WPML support — the best option here if your site is not in English. Small install base (100+) but actively maintained; it was updated the same day this article was written.
AltPost 60 then 15/month
Free registration gives 60 AI-generated images in the first calendar month, then 15 per month, with no API key and no credit card — the AI is handled for you. It has batch controls (start, pause, stop) aimed at WooCommerce and publishers. Worth knowing that it currently shows fewer than 10 active installs, so you would be an early adopter.
Fifteen a month is the smallest ongoing allowance in this group: enough for new uploads on a modest blog, useless against a backlog.
AltText.ai Trial, not a free tier
The best-known dedicated service, and it is paid. New accounts get 25 free credits with no credit card, which is a trial rather than a plan. After that, Bronze is $5/month for 100 credits (5¢ per image), rising to $19 for 500 and $59 for 2,000; one-off credit packs cost $3 for 50. It has a WordPress plugin, bulk generation, CSV import/export and a page scraper.
At 2¢ to 5¢ an image, clearing 2,000 images costs roughly $40 to $100 once. For a business site with a legal deadline, that is often the correct answer — this article is about free options, not about pretending free is always better.
Two Free Routes That Clear a Big Backlog
If the arithmetic above says decades, stop shopping for monthly credits and use one of these instead.
1. Filename-based bulk fill, with no AI and no cap. The plugin "Auto Image Attributes From Filename With Bulk Updater" has 100,000+ active installs, was updated two weeks before this was written, and sets alt text from the image filename for any number of images in one click. No AI, no credits, no ceiling. Its quality is entirely determined by your filenames: blue-ceramic-mug-handle.jpg produces usable alt text, while IMG_4471.jpg produces garbage. Run it on the portion of your library with descriptive filenames, and reserve your AI credits for the rest.
2. Do it yourself with a vision API free tier. Azure AI Vision's free F0 tier includes 5,000 transactions per month at 20 per minute. That is 100 times the most generous plugin allowance, and enough to caption a 5,000-image library inside one billing month. The cost is technical: you need a script that walks the media library, calls the API and writes the results back. If you are comfortable with that, it is the only genuinely free route that finishes a large store, and it pairs well with the CSV import path that services like AltText.ai support — our CSV to JSON converter helps when you need to reshape an export before feeding it back.
Whichever route you pick, audit first so you are not generating text for images that already have it. Screaming Frog SEO Spider is free for crawls of up to 500 URLs, and its Images tab has a "Missing Alt Text" filter with a bulk export of every source page involved. That tells you the real size of the problem before you spend a single credit.
Where AI Alt Text Fails WCAG
Generated alt text passes an automated audit easily. It does not automatically satisfy the standard, and three failure modes are worth knowing before you bulk-apply anything.
Decorative images should have empty alt text, not a description. WCAG 1.1.1 says pure decoration must be implemented so it can be ignored by assistive technology — in practice, alt="". An AI tool looks at your background flourish or divider and dutifully writes "a blue abstract gradient," which a screen reader then reads aloud. That is a worse outcome than leaving it empty, and it is the single most common way bulk generation degrades accessibility while appearing to improve it.
Function beats description for images that do something. For a logo linking to the homepage, the correct alternative names its purpose, not its appearance. AI describes what it sees.
Context is invisible to the model. The same photograph needs different alt text in a news article and a product page. A generator sees pixels, never the surrounding paragraph.
The practical workflow: bulk-generate, then review the output rather than trusting it. Keep descriptions tight — around 125 characters is the usual working limit before screen readers and search engines start truncating, and Word Counter makes that quick to check. If the generated text arrives with odd spacing or stray characters from an export, Remove Extra Spaces and AI Text Cleaner tidy it before it goes into the database.
Comparison Table
| Tool | Free Allowance | 2,000 Images Takes | Watch Out For |
|---|---|---|---|
| AI Alt Text Generator | 50 images/month, no API key or signup | ~3.3 years | Backlog still needs another route |
| Unleash AI | 200 credits/month, "forever free" | ~10 months | Last updated ~2 years ago; untested on recent WP |
| AltTextLab | 25 credits/month, no card | ~6.7 years | Small install base; best for non-English sites |
| AltPost | 60 first month, then 15/month | ~11 years | Fewer than 10 active installs |
| AltText.ai | 25 credits (trial only) | ~$40–100 one-off | Not a free tier; $5/mo for 100 credits |
| Filename bulk updater | Unlimited, free, no AI | One click | Only as good as your filenames |
| Azure AI Vision F0 | 5,000 transactions/month, 20/min | Under a month | You write the script yourself |
Which One Should You Use?
- A normal blog that just needs new uploads covered: AI Alt Text Generator. Fifty a month, nothing to configure, actively maintained.
- A large legacy library and no budget: filename bulk updater first for the images with descriptive filenames, then a monthly free tier for the rest.
- A large library and some scripting ability: Azure's free 5,000 transactions a month finishes the job in one billing cycle.
- A non-English site: AltTextLab, for the 130+ languages and WPML support.
- A business with a compliance deadline: pay AltText.ai. Forty to a hundred dollars once beats three years of waiting.
- Any of them: set decorative images to empty alt text by hand, and spot-check the generated output before it ships.
Alt text is one of three image jobs worth doing in the same pass. While you are in the media library, our guides to compressing images for Core Web Vitals and resizing images correctly cover the other two.