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429 Too Many Requests

4xx client error

The client sent too many requests in a given amount of time — it's being rate limited.

429 is rate limiting. The server — or an API gateway or CDN in front of it — counted your requests, and you went over the allowance. A well-behaved server includes Retry-After (seconds to wait, or a date), often alongside headers that show the quota. A well-behaved client waits that long before trying again instead of hammering the server.

Class4xx Client Error
Retry?With backoff (idempotent requests only)
Cacheable by defaultNo — only with explicit Cache-Control
Response bodyAllowed
Defined inRFC 6585 §4 — 429 Too Many Requests
Example response
HTTP/1.1 429 Too Many Requests
Retry-After: 60
Content-Type: application/json
Content-Length: 29

{"error":"Too Many Requests"}

Common causes

  • Exceeding an API's per-second, per-minute or daily quota.
  • Many parallel requests from one IP address or API key.
  • Retry loops without backoff, which turn one failure into hundreds of requests.
  • Shared IPs — offices, CI runners, cloud NAT — pooling everyone's traffic into one limit.

How to fix it

  1. Honour Retry-After. Without it, back off exponentially with jitter: about 1 s, 2 s, 4 s, plus a random offset.
  2. Cache responses and batch requests to cut volume.
  3. Smooth bursts out with a queue.
  4. If you legitimately need more, ask for a higher quota or a dedicated key.

Useful here: Retries, backoff and Retry-After

Send a 429 from your server

Express
res.set("Retry-After", "60");
res.status(429).json({ error: "Too Many Requests" });
Next.js route handler
return Response.json({ error: "Too Many Requests" }, { status: 429, headers: { "Retry-After": "60" } });
Flask
return {"error": "Too Many Requests"}, 429, {"Retry-After": "60"}
Go net/http
w.Header().Set("Retry-After", "60")
http.Error(w, "Too Many Requests", http.StatusTooManyRequests)
nginx
add_header Retry-After "60" always;
return 429;

Check what a URL returns

Print just the status line from the command line, or check a whole list of URLs at once, with their response headers, in the HTTP Status Checker.

curl -sI https://example.com/your-path | head -n 1

Frequently asked questions

How long should I wait after a 429?

Exactly as long as Retry-After says. Without it, use exponential backoff with jitter and cap the number of retries.

429 vs 503?

429 is about you: this client exceeded its limit. 503 is about the server: it's overloaded or down for everyone. Both may carry Retry-After.

How do I rate limit my own API?

In nginx, use limit_req_zone and limit_req; in Express, middleware such as express-rate-limit. Respond with 429 and Retry-After so clients can recover.

Headers used with 429
Related status codes