Rate Limits & Quotas

SendAPI applies rate limits and monthly quotas to keep the platform stable and fair for all users.

Rate Limits

Rate limits are enforced per API key using a sliding-window token bucket algorithm.

Plan	Requests per minute	Requests per hour
Starter	60	1,000
Growth	600	10,000
Business	6,000	100,000

Rate Limit Headers

Every API response includes these headers:

Header	Description
X-RateLimit-Limit	Maximum requests allowed in the current window
X-RateLimit-Remaining	Requests remaining in the current window
X-RateLimit-Reset	Unix timestamp when the window resets

429 Response

When you exceed the rate limit, the API returns 429 Too Many Requests:

{
  "success": false,
  "error": {
    "type": "rate_limit_exceeded",
    "message": "Too many requests. Please retry after 12 seconds.",
    "code": 4029,
    "retry_after": 12
  }
}

Best practice: Implement exponential backoff when receiving 429. Start at 1s, double each retry, cap at 60s.

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Monthly Quotas

Quotas reset on the first day of each billing period.

Feature	Starter	Growth	Business
WhatsApp messages	1,000	50,000	Unlimited
WhatsApp sessions	1	5	25
SMS messages	Pay-as-you-go	Pay-as-you-go	Pay-as-you-go
Monthly emails	5,000	50,000	500,000
OTP verifications	500	10,000	Unlimited

Quota Exceeded Response

{
  "success": false,
  "error": {
    "type": "quota_exceeded",
    "message": "Monthly WhatsApp message quota exceeded. Upgrade your plan to continue.",
    "code": 4028,
    "upgrade_url": "https://sendapi.co/billing"
  }
}

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Per-Endpoint Limits

Some endpoints have additional per-session rate limits independent of your plan:

Endpoint	Limit
WhatsApp messages per session	30/min, 1,000/day
OTP send per phone	5/hour, 20/day
Webhook test triggers	10/hour