429 Too Many Requests
The server or a firewall is rate-limiting: this client sent more requests than allowed in a time window.
Where it failed: the request
What visitors see
A "Too Many Requests" page, or a blank page, often with a Retry-After header.
Usual causes
- A rate-limiting rule (Cloudflare, nginx limit_req, an API gateway) is too tight for real traffic.
- Many visitors share one address (an office, a mobile carrier's NAT) and count as one client.
- A bot or a script really is sending too many requests.
How to tell which one it is
- The Retry-After header says how long to wait.
- The firewall's log shows which rule and which client.
What to do
- Raise the limit or key it on something better than the IP (a session, an API key).
- Exempt your own monitoring and known good bots.
- For an API, document the limit and send RateLimit headers.
Check the site now
The Down Checker names the layer that failed (DNS, connection, TLS or the server) and decodes the error page it gets.
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