Captcha Generation
The /captcha endpoint generates a CAPTCHA image. You can provide your own text or let the API generate a random one automatically.
GET/v4/captcha
Parameters
| Parameter | Required | Description |
|---|---|---|
text | No | The captcha text. If omitted, a random string is generated |
length | No | Length of the auto-generated text (default 6) |
width | No | Image width in pixels (default 300) |
height | No | Image height in pixels (default 150) |
noise | No | Number of noise lines (default 5) |
bg | No | Background color in hexadecimal (e.g. ffffff) |
color | No | Text color in hexadecimal (e.g. 000000) |
Response
The endpoint returns a PNG image of the generated captcha.
Good to know
The response includes an X-Captcha-Text header containing the captcha answer, useful for server-side verification. When no text is provided, the auto-generated string avoids ambiguous characters (e.g. 0/O, 1/l).
Code Examples
curl -X GET \
"https://api.sylvain.sh/v4/captcha?length=8&width=400&noise=high&bg=f0f0f0"Try It
Error Handling
If parameters are missing or invalid, the API will return an error:
| Error Message | Description |
|---|---|
length must be a number | The length parameter is not a number |
length must be between 1 and 20 | The length is out of range |
width must be a number | The width parameter is not a number |
width must be between 100 and 800 | The width is out of range |
height must be a number | The height parameter is not a number |
height must be between 50 and 400 | The height is out of range |
noise must be one of: low, medium, high | Invalid noise value |
Invalid color (use hex like ff6600) | A bg or color parameter is malformed |