• Version 3.0+ is only compatible with projects created in or imported to the new Firebase Console.
• The Firebase CLI now uses direct Google OAuth2 login. All users must re-authenticate.
• The -f/--firebase option has been renamed to -P/--project and refers to project id, not instance name.
• The firebase deploy:* commands have been replaced with firebase deploy --only * with a list of features.
• The firebase data:* commands have been renamed to firebase database:* commands.
• The firebase disable:hosting command has been renamed to firebase hosting:disable.
• firebase init now initializes multiple features and can be re-run in an existing project directory.
• firebase open no longer just opens Hosting site, now provides a selection of useful project URLs.
• firebase prefs:token is removed in favor of firebase login:ci
• firebase tools:migrate is available to update firebase.json to current schema.
• firebase use is now available for managing project environment aliases in a project directory.
• The Firebase CLI can now deploy rules for Firebase Storage.
• Improved port-finding behavior of firebase serve.
• The firebase key in firebase.json is now deprecated in favor of firebase use.