This extension adds an icon to Firefox’s address bar which indicates whether this page used Encrypted-Client-Hello (ECH) or not.
ECH is a extension to TLSv1.3 which encrypts the TLS Client-Hello. Before ECH any middle-man between your PC and the server was able to read out the SNI (Server-Name-Indication), i.e. the domain you were visiting.
The extension displays a green/red-lock to the right side of your address bar, similar to the HTTP(S) lock.
