529 Site is overloaded

This is an educational reference page about HTTP 529 Site is overloaded. The page itself is served as 200 OK so it can be indexed as HTTP documentation.

Used by Qualys in the SSLLabs server testing API to signal that the site can't process the request.

What it means

HTTP 529 Site is overloaded means the server or upstream service is too busy to process the request right now.

Common causes

A service-specific overload condition rejects new work.
Queue depth, worker capacity, or dependency limits are temporarily exhausted.
An API uses 529 as a non-standard overload signal instead of 503.

How to fix it

Retry later with exponential backoff and jitter.
Reduce request concurrency or batch size from the client.
Prefer 503 with Retry-After for general HTTP clients unless your API contract specifically documents 529.

Example response

HTTP/1.1 529 Site is overloaded
Retry-After: 30
Content-Type: application/json

{"error":"site_overloaded"}

Developer notes

529 is not a standard core HTTP status code. Treat it like a temporary overload response when you encounter it in a documented API.

Questions

What does HTTP 529 mean?

HTTP 529 means a site or API is overloaded and cannot process the request at the moment.

Is 529 a standard HTTP status code?

No. 529 is non-standard and service-specific. 503 is the standard temporary-unavailable status.