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Integrate our tools directly into your apps, scripts, and workflows. Simple REST endpoints, JSON responses, zero dependencies.
QR codes, hashing, passwords, JSON, colors, UUIDs, and more.
Simple Bearer token authentication. Get a key instantly.
All endpoints return JSON with CORS enabled for any origin.
All API requests require an API key. Pass it in the Authorization header or as a query parameter.
Header (recommended)
Authorization: Bearer ot4f_test_YOUR_KEYQuery parameter
GET /api/v1/uuid?count=5&api_key=ot4f_test_YOUR_KEYGet your API key — Sign up for a Pro account to receive your API key with 10,000 calls/month included.
| Tier | Key prefix | Requests/month |
|---|---|---|
| Free | ot4f_free_* | 500 |
| Pro / Dev | ot4f_test_* | 10,000 |
All errors return a JSON object with an error field and the appropriate HTTP status code.
// Error response format
{ "error": "Description of what went wrong" }200Success400Bad request — missing or invalid parameters401Unauthorized — missing or invalid API key429Rate limit exceeded500Server errorGenerate a QR code as SVG.
| Name | Type | Required | Description |
|---|---|---|---|
| data | string | Yes | The text or URL to encode |
| fgColor | string | No | Foreground color (default: #000000) |
| bgColor | string | No | Background color (default: #FFFFFF) |
| errorCorrection | L|M|Q|H | No | Error correction level (default: M) |
curl -X POST "https://onlinetools4free.com/api/v1/qr-code" \
-H "Authorization: Bearer ot4f_test_YOUR_KEY" \
-H "Content-Type: application/json" \
-d '{"data":"https://example.com","fgColor":"#000000","bgColor":"#FFFFFF","errorCorrection":"M"}'{ "svg": "<svg ...>...</svg>", "modules": 25 }Get your API key and start making requests in under a minute.
Get your API key