curl/docs/cmdline-opts/ech.md

c	SPDX-License-Identifier	Long	Arg	Help	Added	Category	Protocols	Multi	See-also	Example
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.	curl	ech	<config>	Configure ECH	8.8.0	tls ECH	HTTPS	single	doh-url	--ech true $URL

--ech

Specifies how to do ECH (Encrypted Client Hello).

The values allowed for <config> can be:

"false"

Do not attempt ECH

"grease"

Send a GREASE ECH extension

"true"

Attempt ECH if possible, but do not fail if ECH is not attempted. (The connection fails if ECH is attempted but fails.)

"hard"

Attempt ECH and fail if that is not possible. ECH only works with TLS 1.3 and also requires using DoH or providing an ECHConfigList on the command line.

"ecl:"

A base64 encoded ECHConfigList that is used for ECH.

"pn:"

A name to use to over-ride the public_name field of an ECHConfigList (only available with OpenSSL TLS support)

Errors

Most errors cause error CURLE_ECH_REQUIRED (101).