Guides

Limits

Rate Limits

All Skribble APIs enforce rate limiting. Exceeding a limit returns 429 Too Many Requests. Requests resume once the rate limit window resets.

General Behaviour

Every endpoint can return a 429 response. When you receive one:

1. Stop sending requests to that endpoint immediately.
2. Check the Retry-After header (if present); it indicates how many seconds to wait.
3. Back off exponentially if no header is present (e.g. 1 s → 2 s → 4 s → …).
4. Retry once the wait period has elapsed.

Known Per-Endpoint Limits

Endpoint	Limit
POST /access/login	Rate limited; avoid re-authenticating on every request; cache tokens for their ~20-minute lifetime.
POST /signature-requests/{id}/remind	One reminder per signer per hour. The API enforces this server-side; exceeding it returns 429. Track reminder timestamps client-side to avoid unnecessary calls.

Recommended Client Behaviour

Code
async function requestWithBackoff(fn, maxRetries = 5) {
  for (let attempt = 0; attempt < maxRetries; attempt++) {
    const res = await fn();

    if (res.status !== 429) return res;

    const retryAfter = Number(res.headers.get('Retry-After') || 0);
    const wait = retryAfter > 0 ? retryAfter * 1000 : Math.pow(2, attempt) * 1000;
    await new Promise(r => setTimeout(r, wait));
  }

  throw new Error('Rate limit retries exhausted');
}

Document Size Limits

Sign API

Constraint	Limit
Documents per signature request	50
Max document size (unencoded)	112.5 MB
Max document size (Base64 encoded)	150 MB

Documents must be Base64-encoded when sent to the API. Base64 introduces a size overhead of approximately 33%:

Code
unencoded × 4/3 = encoded size
e.g. 112.5 MB × 4/3 = 150 MB

Ensure your document does not exceed 112.5 MB before encoding.

Validation API

Constraint	Limit
Document size (multipart upload)	50 MB
Document size (Base64 JSON payload)	50 MB (Base64 overhead is handled automatically)
Request size	50 MB

Attachments

There is currently no documented limit on the number of attachments per signature request. Abusive usage may result in enforced limits.

Performance Tips

1. Batch document uploads: Upload documents in parallel before creating requests
2. Cache authentication tokens: Reuse tokens until they expire
3. Use pagination: When listing requests, use page_number and page_size
4. Poll efficiently: Use callbacks instead of polling when possible