App Veil

App Veil hides windows from your pair while you're sharing your screen. It can also hide all system notifications while you're pairing with the "Hide all notifications" setting.

Hidden windows have a dashed orange border around them to remind you they're not shared:

You can configure this feature in Tuple's Settings. By default, we hide Messages, and Keychain Access. We also hide Telegram, and 1Password if you have those apps installed.