curl-w32/docs/cmdline-opts/anyauth.md

c	SPDX-License-Identifier	Long	Help	Protocols	Category	Added	Multi	See-also	Example
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.	curl	anyauth	Pick any authentication method	HTTP	http proxy auth	7.10.6	mutex	proxy-anyauth basic digest	--anyauth --user me:pwd $URL

--anyauth

Tells curl to figure out authentication method by itself, and use the most secure one the remote site claims to support. This is done by first doing a request and checking the response-headers, thus possibly inducing an extra network round-trip. This is used instead of setting a specific authentication method, which you can do with --basic, --digest, --ntlm, and --negotiate.

Using --anyauth is not recommended if you do uploads from stdin, since it may require data to be sent twice and then the client must be able to rewind. If the need should arise when uploading from stdin, the upload operation fails.

Used together with --user.