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4xx Client Error
What it means
The client has sent too many requests in a given time period (rate limiting).
| Property | Detail |
|---|---|
| Status class | 4xx Client Error |
| Defined in | RFC 6585, Section 4 |
| Cacheable by default | No. RFC 6585 states that responses with the 429 status code must not be stored by a cache. |
| Who needs to act | The client, which has to slow down. |
What does HTTP 429 Too Many Requests mean?
HTTP 429 Too Many Requests means the client sent too many requests in a given amount of time and is being rate limited. The server may include a Retry-After header giving a number of seconds or a date. Waiting that long, then retrying with backoff, is the correct response; retrying immediately only makes things worse.
How 429 Too Many Requests works
RFC 6585 deliberately leaves the details to the server. It does not define how the client is identified or how requests are counted, so a limit can apply per API key, per user, per IP address, per endpoint or across a whole service. The response should explain the condition and may include Retry-After. Many APIs also send non-standard headers such as X-RateLimit-Limit, X-RateLimit-Remaining and X-RateLimit-Reset so clients can pace themselves before reaching the limit. The RFC also notes that a server under attack does not have to send 429 at all, and may simply drop connections instead.
Example 429 request and response
GET /api/search?q=status HTTP/1.1
Host: api.example.com
Authorization: Bearer <access-token>
HTTP/1.1 429 Too Many Requests
Retry-After: 30
Content-Type: application/jsonRetry-After: 30 asks the client to wait 30 seconds. It could equally be an HTTP date, such as Wed, 21 Oct 2026 07:28:00 GMT.
What causes a 429 Too Many Requests
- Bursts of API calls from loops, retries or many parallel workers.
- Several services sharing one API key or one outbound IP address.
- Retry logic without backoff, which turns one failure into a storm of requests.
- Scrapers and crawlers fetching faster than a site permits.
- Login and one-time-code endpoints throttling repeated attempts.
How to fix a 429 Too Many Requests
If you are being rate limited
- Honour Retry-After whenever it is present.
- Otherwise use exponential backoff with jitter: double the wait after each further 429 and add randomness so clients do not retry in sync.
- Reduce concurrency, cache responses you reuse, and batch requests where the API allows it.
If you run the API
- Send Retry-After and a message naming the limit that was hit.
- Expose remaining-quota headers so well-behaved clients can pace themselves.
- Rate limit per key or per user, not only per IP, so shared networks are not punished.
429 and SEO
Google's crawlers treat 429 as a sign of server overload rather than as a normal 4xx: they slow down, already indexed URLs are kept for the time being, and crawling speeds up again once the errors stop. Google suggests returning 429, 500 or 503 to reduce crawl rate only in an emergency lasting a day or two; if the same URLs keep returning them for several days, they may be dropped from the index. Do not use 403 to slow Googlebot down.
Related status codes
- 503 Service Unavailable: The whole service is overloaded or down, not just this one client.
- 403 Forbidden: Access is refused outright rather than paced; a poor substitute for rate limiting.
Frequently asked questions
The client has sent too many requests in a given time period (rate limiting).
Exceeding an API's rate limit by sending requests too frequently.
Slow down your request rate. Check the response's Retry-After header for how long to wait before retrying.
If the response has a Retry-After header, wait that long: it is either a number of seconds or a date. If it does not, back off exponentially, for example 1, 2, 4 and then 8 seconds, with some random jitter, and cap the number of retries.
Sources
- RFC 6585, Section 4
- RFC 9110, Section 10.2.3 (Retry-After)
- Google: How HTTP status codes affect Google's crawlers
- Google: Reduce the Google crawl rate
Other 4xx Client Error codes
Reviewed by Raja Jahangir · Last reviewed: October 7, 2026