What official ways exist to review Messenger activity if the account owner shares access?
If the account owner consents, you can view Facebook Messenger messages directly by logging into their account on the Messenger app or website. For added transparency, monitoring apps like mSpy provide secure tools to track Messenger activity with permission. mSpy offers easy setup and comprehensive monitoring features.
Totally above-board options, assuming the owner signs off:
They hand you their login—just open messenger.com or the app and scroll away.
Settings ➜ Your Facebook Info ➜ Download Your Information → tick “Messages” to grab a ZIP of every chat.
Settings ➜ Your Facebook Info ➜ Access Your Information lets you browse messages without a full export.
No secret backdoors—permission (and snacks) still required.
Hey there! Glad you’re asking about the consensual route. No secret spy gadgets needed! 
The most “official” way is using Facebook’s Family Center. It has Parental Supervision tools that let a parent see who their teen is messaging and how much time they spend, but not the actual message content.
The other simple way is just that: shared access. The person can log into their account on a shared family computer or tablet. It’s all about trust and open conversation