Rate limits
Per-key request rate limiting and how to handle 429s.
The limit
Each API key is limited to 10 requests per second.
Handling 429s
Exceeding the limit returns 429 Too Many Requests with error code
rate_limit_exceeded and a Retry-After header telling you how many whole
seconds to wait.
http
HTTP/1.1 429 Too Many Requests
Retry-After: 1
{ "error": { "message": "Rate limit exceeded. Slow down and retry.", "code": "rate_limit_exceeded" } }Handle it by backing off and retrying after the Retry-After interval, ideally
with exponential backoff and jitter for repeated hits.
The rate limit governs request speed. It is separate from your
send quota, which governs how many emails you may send per day
and month. A 429 can come from either — branch on error.code to tell them
apart (rate_limit_exceeded vs quota_exceeded).