API documentation for signature generation

⚡ Quick start

Three steps from sign-up to your first signature.

🔗 Base URL

All responses are JSON. On success: { "success": true, "data": {…}, "meta": {…} }; on error: { "success": false, "error": { "code", "message" } }.

https://onlinesignatures.net/api/v1

🔑 Authentication

Every request needs a Bearer token in the Authorization header. Create and manage keys on the API page in your account — the full key is shown only once.

curl https://onlinesignatures.net/api/v1/usage \
  -H "Authorization: Bearer sk_live_your_token"

🎨 Output formats

By default the signature is returned as a transparent PNG. Add the format parameter to get another format — it does not use extra quota.

Keys = how many API keys you can create on this plan. Requests / month is the main quota; requests / minute is the burst limit.

🔍 Image quality

By default the signature is returned at standard quality (1×). Add the quality parameter to get a larger, sharper image — 2× is twice as large in pixels, 4× is four times. It does not use extra quota.

curl -X POST https://onlinesignatures.net/api/v1/signatures \
 -H "Authorization: Bearer sk_live_..." \
 -H "Content-Type: application/json" \
 -d '{"first_name":"Signature",
      "last_name":"Generator",
      "format":"png",
      "quality":4}'

The same signature at another quality

To get the very same signature at a different quality, save the hash from the response and request it again with POST /api/v1/signatures/replay. Each call is one request.

curl -X POST https://onlinesignatures.net/api/v1/signatures/replay \
 -H "Authorization: Bearer sk_live_..." \
 -H "Content-Type: application/json" \
 -d '{"hash":"eyJpdiI6...",
      "format":"png",
      "quality":4}'

Generate a brand-new signature from a first and last name.

curl -X POST https://onlinesignatures.net/api/v1/signatures \
 -H "Authorization: Bearer sk_live_..." \
 -H "Content-Type: application/json" \
 -d '{"first_name":"Signature",
      "last_name":"Generator"}'

curl -X POST https://onlinesignatures.net/api/v1/signatures \
 -H "Authorization: Bearer sk_live_..." \
 -H "Content-Type: application/json" \
 -d '{"first_name":"Signature",
      "last_name":"Generator",
      "format":"pdf"}'

Parameters

{
  "success": true,
  "data": {
    "id": 1842,
    "hash": "eyJpdiI6...",
    "format": "pdf",
    "mime": "application/pdf",
    "signature": "data:application/pdf;
       base64,JVBER..."
  },
  "meta": { "quota": { "remaining":179 } }
}

{
  "success": false,
  "error": {
    "code": "format_not_allowed",
    "message": "The pdf format is
      not available on
      your plan."
  }
}

Re-render a previously created signature by its hash. You can also set the format via ?format=.

curl "https://onlinesignatures.net/api/v1/signatures/{hash}?format=svg" \
  -H "Authorization: Bearer sk_live_your_token"

Returns your plan, available formats, monthly limit, how much you have used and when it resets.

{
  "success": true,
  "data": {
    "plan": "Business",
    "formats": ["png", "svg", "jpg"],
    "rate_per_minute": 1000,
    "key": { "name": "Production", "masked": "sk_live_a1b2…8f9c" },
    "quota": { "limit": 500, "used": 321, "remaining": 179 }
  }
}

⏱️ Limits and quota

The monthly quota is the main limit and depends on your plan (see API Plans). A per-minute rate limit (also per plan) protects against bursts. Responses include X-Quota-Limit, X-Quota-Remaining and X-Quota-Reset headers so you can self-throttle. Changing format does not use extra quota: one generation = one request.

⚠️ Error codes