4xx · Client errorretryable
429Too Many Requests
The user has sent too many requests in a given amount of time. Intended for use with rate-limiting schemes.
What this code obliges you to do
Retry
Safe to retry
Repeating the same request can succeed, so a client may back off and try again. Honour Retry-After when the response sends one.
Caching
Not cacheable by default
Caches will not store this response unless you send explicit freshness headers saying they may.
Response body
Body allowed
You may return a payload explaining the outcome — for an error, a machine-readable problem document is worth the effort.
What usually causes it
31
API rate limiting (RateLimit-Limit headers)
2
DDoS mitigation active
3
Aggressive web scraping
Effect on search
Can be negative if Googlebot hits crawl limits. Use the Retry-After header so Googlebot knows exactly when to come back.
How to send it
1Node.js (Express)
res.status(429).send('Rate limit exceeded');Codes people confuse with this one
1Class4xx
RetrySafe
CacheNo
BodyAllowed