jargon

Frontend & browser·The network from the browser

the network panel shows an OPTIONS request before your PUT, and the PUT never happened because it failed.

Preflight request

Also calledOPTIONS preflight

An automatic `OPTIONS` request the browser sends before a cross-origin request that is not simple, asking whether the method and headers are permitted. It doubles the round trips for those requests unless the response is cached with `Access-Control-Max-Age`. Adding a custom header or a JSON content type to a request that did not need one before is the usual way a working call suddenly acquires a preflight.

Commonly confused with