Is 507 widely supported?

It is in the HTTP spec and used by some WebDAV servers and a handful of REST APIs. Many APIs use 503 or a custom error code instead.

507 Insufficient Storage: HTTP Status Code Meaning, Causes, and Fixes

What 507 Insufficient Storage means

507 Insufficient Storage is a WebDAV code that some non-WebDAV APIs adopt for "out of disk space" or "quota exceeded" scenarios. It is more specific than 500 (the server is broken) or 503 (the service is unavailable): 507 says "the storage layer specifically cannot accept this".

When servers should return it: Return 507 when storage is full or quota is exceeded.

Common causes

Disk full on the storage server
User storage quota exhausted
Database tablespace full

How to fix 507 Insufficient Storage

Free up storage
Increase quota
Delete old data before retrying

Example response

HTTP/2 507
content-type: application/json
{"error":"quota exceeded","used_gb":100,"quota_gb":100}

More references

For a one-page reference of all HTTP status codes, see the HTTP cheat sheet. For testing API responses, try the API Tester tool. For inspecting responses on the command line, the curl cheat sheet covers the most common flags.