HTTP 508 Loop Detected

The server stopped processing because it detected an infinite loop — typically a resource that, directly or indirectly, includes itself.

Defined in RFC 5842 §7.2 — 508 Loop Detected · MDN reference

Where you meet HTTP 508 in production

WebDAV servers walking bindings that contain themselves, and some hosting platforms that report a request bouncing between their own services.

Why you would test it

A useful check that your client does not retry indefinitely on a server error that will never resolve on its own.

What your client should do about a 508

Do not retry; the loop is in the server's data or configuration. Fix the cycle — a binding, a self-referencing configuration, or a proxy forwarding to itself.

508 versus the codes it gets confused with

Endpoints that return 508

1 endpoint in this playground answers with 508. Every one is free, needs no signup, and can be called from the browser or with curl.

Questions about HTTP 508

Is 508 a redirect loop?
No. Redirect loops are detected by clients. 508 is a loop the server detected while processing.
Where is 508 defined?
In the WebDAV binding extension, RFC 5842.

Other server error codes

All HTTP status codes · All 39 mock REST APIs · Getting started guide

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