Generate alt text
A product catalog with three thousand images and zero alt text is invisible to screen readers and to image search alike. The alt text generator API looks at each image and writes a concise, natural-language description built to serve both purposes at once — genuine accessibility for people using assistive technology, and a real, keyword-relevant signal for search engines that can't see pixels. Send an image, get back a description ready to drop into an alt attribute.
Run it online
Run this on our servers with your account. Free tools run in your browser; this one bills your KIT balance per the price above.
One piece of markup, two audiences
The alt attribute was written into HTML from the start as a fallback for when an image couldn't load, but it became the primary way screen reader software conveys visual content to blind and low-vision users, and later a genuine ranking signal for image search. Those two audiences — assistive technology and search crawlers — want the same thing: a short, accurate sentence describing what's actually in the picture, not a stuffed list of keywords. This endpoint writes for both at once, because good alt text always has served both.
What the description covers
POST an image to /image/describe and the task returns a plain-language description that identifies the main subject, relevant visible details and context, phrased as a complete, natural sentence rather than a fragment. It's built to read the way a person would describe the image aloud to someone who can't see it — specific enough to be useful, short enough to stay usable inside an alt attribute.
Where teams put this to work
The most common trigger is a backlog: an e-commerce catalog migrated from a platform that never captured alt text, a media library with years of uploads and no description field filled in, a CMS that made alt text optional and nobody filled it in. Because the task runs asynchronously, it processes a backlog in batches without tying up a request thread, landing results by webhook as each image finishes, or via a signed link for a script that prefers to pull results on its own schedule.
An accessibility requirement, not a nice-to-have
Accessibility guidelines have required meaningful alt text for images for decades, and increasingly it's treated as a baseline compliance requirement rather than a stretch goal. Generating it automatically doesn't replace a human reviewing genuinely important images — a hero banner or a chart carrying real information still deserves a human eye — but it closes the gap on the thousands of routine product and content images that would otherwise stay undescribed forever.
Pricing built for catalog-scale work
The cost combines a small flat fee per request with a per-image charge, so describing one hero image and running ten thousand product photos through the same endpoint both scale honestly with the work performed. A failed description is retried automatically up to three times and never billed if it still can't complete, so a backlog run only costs you for the descriptions that actually land.
What you can do with it
E-commerce catalog backfill
An online store with thousands of product photos and no alt text runs its entire catalog through the endpoint overnight to close an accessibility and SEO gap in one pass.
CMS publishing workflow
A publishing platform auto-generates a draft alt text description the moment an editor uploads an image, saving a manual writing step on every article.
Legacy media library cleanup
A company migrating a decade-old media library uses the endpoint to generate missing descriptions for assets that predate any alt text requirement.
Accessibility compliance audit remediation
A team responding to an accessibility audit finding generates alt text for every flagged image as part of a documented remediation pass.
FAQ
How does the alt text generator API write descriptions?
It analyzes the visible content of each image and produces a concise, natural-language sentence describing the main subject and relevant details, phrased for direct use in an alt attribute.
Is the generated alt text actually good for SEO?
It describes what's genuinely in the image using natural phrasing rather than keyword stuffing, which is exactly what search engines reward and what accessibility guidelines require — the two goals align rather than conflict.
Can it process a large product catalog in bulk?
Yes, each image is one request and the task is asynchronous, so a script can submit thousands of images and collect results via webhook as each one finishes without holding anything open.
Does this replace a human writing alt text for important images?
For high-stakes images like data charts or key marketing banners, a human review is still worthwhile; the endpoint is built to efficiently cover the large volume of routine images that would otherwise go undescribed.
Is the alt text generator API free to use?
There's no free tier — free tiers get abused and slow everyone down. Access runs on a prepaid ForHosting KIT balance: top up from $10.00 (it never expires) and each request is charged at its published price, so a call with no balance returns HTTP 402. No subscription, no tokens, no invented credits, and a failed task is never charged.
How long does it take to get results back?
The task returns a task_id immediately and processes asynchronously; the description arrives via signed webhook, or you can retrieve it from a signed link valid for 24 hours.
What image formats are supported?
JPEG, PNG and WebP images are supported as input for description generation.
What happens if a description generation fails?
The task retries automatically up to three times before returning a clear error, and a failed request is never charged.
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, and soon from our app, email and Telegram.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/image/describe \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"image":"https://ejemplo.com/imagen.jpg"}'const res = await fetch("https://api.kit.forhosting.com/image/describe", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"image": "https://ejemplo.com/imagen.jpg"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/image/describe",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"image": "https://ejemplo.com/imagen.jpg"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/image/describe", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"image":"https://ejemplo.com/imagen.jpg"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"image":"https://ejemplo.com/imagen.jpg"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/image/describe", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"image": "https://ejemplo.com/imagen.jpg"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "image.describe",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_mb | 15 |
max_megapixels | 12 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
422 | task_failed | The task failed after 3 retries. You are never charged for it. |