Image Caption is an AI-powered tool that generates descriptive captions for images. Simply upload an image and receive a natural language description of its contents.
Try it — live request, no key required
No key required to try it. Get a key to use it in your app.
{
"status": "ok",
"error": null,
"data": {
// Image Caption response payload
}
}
About the Image Caption API
Supports common image formats including JPG, PNG, and GIF. Images are automatically resized for optimal processing. Maximum file size is 5MB.
What people use it for
- Accessibility
- Generate alt text for images to improve web accessibility for visually impaired users
- Content Management
- Automatically generate descriptions for large image libraries and media assets
- Social Media
- Create engaging captions for social media posts and marketing content
- Search Optimization
- Improve image searchability by generating descriptive metadata
Ways to call it
One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.
- JSON
- Default REST response
- XML
- Markup format
- YAML
- Human-readable
- CSV
- Tabular export
- GraphQL
- Query language
- MCP
- For AI agents
What does the Image Caption API do?
How do I authenticate Image Caption API requests?
How much does the Image Caption API cost?
How fast is the Image Caption API?
What response formats does the Image Caption API support?
What HTTP method does the Image Caption API use?
Request parameters — POST /v1/imagecaption
Sent as JSON in the request body. Premium parameters are accepted on every plan but only take effect on plans that include them. Anything not listed here is dropped rather than passed through.
Required
| Parameter | Type | Example | Description |
|---|---|---|---|
imageRequired | string | Upload an image file to generate a caption (supported formats: JPG, PNG, GIF, max 5MB) |
curl -X POST "https://api.apiverve.com/v1/imagecaption" \
-H "x-api-key: YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{}'Authentication
Send your key in the x-api-key header. That is the only auth step — no token exchange, and no per-endpoint scope to configure.
| Header | When | Value |
|---|---|---|
x-api-keyRequired | Every request | Your API key. Header names are case-insensitive, so X-API-Key is the same header. |
AuthorizationAlternate | Instead of the above | Bearer <key> — for clients that only expose bearer auth. Resolves to the same account and the same billing. |
content-typeRequired | POST body | application/json |
A 401 means the key is missing, invalid or expired. A 403 means the key is valid but not permitted here — blocked by a key restriction or an IP allow-list. Running out of credits is a 429.
Response — POST /v1/imagecaption
Every APIVerve endpoint returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape.
{
"status": "ok",
"error": null,
"data": {
"caption": "A golden retriever running through a grassy field on a sunny day"
}
}
Response fields
Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.
| Field | Type | Example | Description |
|---|---|---|---|
caption | string | "A golden retriever running through a grassy field on a sunny day" | AI-generated natural language description of image contents |
Response headers
Every response carries your balance, so your own code always knows where it stands without polling anything. All four are exposed to browsers through CORS.
| Header | What it carries |
|---|---|
x-api-remaining-credits | Credits left in the current cycle |
x-api-credits-used | Credits spent in the current cycle |
x-api-max-credits | The allowance for the cycle |
x-api-version | Version of the endpoint that answered |
Errors
Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change.
| Status | Meaning | What to do |
|---|---|---|
400 | Input was rejected | Read error; it names the parameter that has to change. |
401 | Key missing or invalid | Check the header name and the key value. |
403 | Key valid, but not permitted here | A key restriction or an IP allow-list — never a bad key. |
429 | Rate limited, or out of credits | Read error to tell them apart, then back off or top up. |
What a call costs — 20 credits per call
Credits are shared across every APIVerve API — one balance, one key, one bill. Failed requests never count against it, so a rejected input costs nothing.
| Plan | Per month | Credits | Image Caption calls | Per 1,000 calls |
|---|---|---|---|---|
| Free | Free | 200 | 10 | Free |
| Starter | $29.99 | 200,000 | 10,000 | $3.00 |
| Pro | $99.99 | 1,000,000 | 50,000 | $2.00 |
| Mega | $299.99 | 4,000,000 | 200,000 | $1.50 |
Calls are what the credits buy at this API's rate — spend them here, on any of the other APIs, or across both. Nothing is reserved per endpoint.
Call it from cURL — POST /v1/imagecaption
No SDK to install — this is a plain HTTPS call to /v1/imagecaption with your key in the x-api-key header. Swap in a real key and it runs as-is.
curl "https://api.apiverve.com/v1/imagecaption" \
-H "x-api-key: YOUR_API_KEY"Resources
Also published for
Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.
Call it from Node.js — POST /v1/imagecaption
Install the Node.js SDK, then call the Image Caption API with your key. The client wraps the same HTTPS request, so anything it returns is what the endpoint returns.
npm install @apiverve/imagecaptionconst res = await fetch("https://api.apiverve.com/v1/imagecaption", {
headers: { "x-api-key": "YOUR_API_KEY" },
});
const { data } = await res.json();
console.log(data);Resources
Also published for
Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.
Call it from Python — POST /v1/imagecaption
Install the Python SDK, then call the Image Caption API with your key. The client wraps the same HTTPS request, so anything it returns is what the endpoint returns.
pip install apiverve-imagecaptionimport requests
res = requests.get(
"https://api.apiverve.com/v1/imagecaption",
headers={"x-api-key": "YOUR_API_KEY"},
)
print(res.json()["data"])Resources
Also published for
Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.
Call it from C# / .NET — POST /v1/imagecaption
Install the C# / .NET SDK, then call the Image Caption API with your key. The client wraps the same HTTPS request, so anything it returns is what the endpoint returns.
dotnet add package APIVerve.API.ImageCaptionusing var client = new HttpClient();
client.DefaultRequestHeaders.Add("x-api-key", "YOUR_API_KEY");
var json = await client.GetStringAsync("https://api.apiverve.com/v1/imagecaption");
Console.WriteLine(json);Resources
Also published for
Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.
Call it from Go — POST /v1/imagecaption
No SDK to install — this is a plain HTTPS call to /v1/imagecaption with your key in the x-api-key header. Swap in a real key and it runs as-is.
req, _ := http.NewRequest("GET", "https://api.apiverve.com/v1/imagecaption", nil)
req.Header.Set("x-api-key", "YOUR_API_KEY")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))Resources
Also published for
Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.
Call it from PHP — POST /v1/imagecaption
No SDK to install — this is a plain HTTPS call to /v1/imagecaption with your key in the x-api-key header. Swap in a real key and it runs as-is.
$ch = curl_init("https://api.apiverve.com/v1/imagecaption");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-api-key: YOUR_API_KEY"]);
$response = curl_exec($ch);
echo $response;Resources
Also published for
Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.
Call it from Ruby — POST /v1/imagecaption
No SDK to install — this is a plain HTTPS call to /v1/imagecaption with your key in the x-api-key header. Swap in a real key and it runs as-is.
require "net/http"
uri = URI("https://api.apiverve.com/v1/imagecaption")
req = Net::HTTP::Get.new(uri)
req["x-api-key"] = "YOUR_API_KEY"
res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |h| h.request(req) }
puts res.bodyResources
Also published for
Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.
Zero-code embed — one snippet, no backend
Drop an interactive Image Caption form onto any page. The widget calls the API for you, so no key ever appears in your markup and there is nothing to deploy.
Changelog — Image Caption API
Every change to this endpoint, newest first. Breaking changes ship as a new version and the previous one keeps serving — response fields are added, never removed or retyped in place, so an integration written against v1 keeps working.
Entries are picked up from dated catalog snapshots, so the first one appears after the next snapshot that moves something. A period where nothing changed produces no entry — silence is a valid changelog for the Image Caption API.
AI/Computer Vision
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