The HTTP 429 status code means a client has sent too many requests.
API services typically rate-limit requests to prevent abuse or to sell access to more expensive plans with fewer restrictions. Rate limits are usually implemented using API keys, but it is not uncommon to limit requests by IP address or user-agent.
When a client reaches a certain threshold of requests (for example, 420 requests in one hour), a server that wants to rate-limit the client will send the
429 Too Many Requests status code.
The server might respond with the
Retry-After HTTP header, asking a client to retry a request after a certain period.
Some services include HTTP headers like
X-RateLimit-Reset to inform clients about a limit, how many requests remain before the limit kicks in, and when the limit resets, respectively.