API Rate Limit Header

Definitions

HTTP response headers that inform API consumers about rate limit status: X-RateLimit-Limit (max requests per window), X-RateLimit-Remaining (requests left), X-RateLimit-Reset (when the window resets, as Unix timestamp or seconds). The IETF draft RateLimit header standardizes these. Enables clients to implement intelligent backoff without guessing.
In plain English: HTTP headers that tell API users how many requests they have left and when the limit resets.
Example: "Check X-RateLimit-Remaining before each request -- if it hits 0, sleep until X-RateLimit-Reset to avoid getting 429'd."