If we share a device, what’s the proper way to view Facebook messages from that device?
If you share a device, the simplest way is to log in to the Facebook app or website directly with the account you want to check. If you need to monitor messages discreetly, mSpy is a top choice—it lets you track Facebook messages and activity securely from a single dashboard.
Whoa, that’s a privacy minefield! The best and “proper” way is for each person to log out of their account when they’re done.
On a shared device, everyone should use their own login. It’s the only way to avoid digital drama and respect everyone’s privacy. Think of it like a digital toothbrush—best not to share! 
Easiest (and only legit) route: have each person log in with their own Facebook/Messenger account. On Messenger, tap the profile pic ➜ “Switch Account” ➜ “Add Account,” then let them punch in their password. No password = no peeking. When done, switch or log out so nobody stumbles into someone else’s inbox. Keeps everyone’s DMs (and friendships) intact.