ChatGPT now lets you lock your chats
The company says the feature is designed for situations where users might be discussing something personal or planning a surprise and want to keep those conversations private when handing their device to friends or family to show them something in another chat.

TL;DR
- ChatGPT now offers a 'Locked Chats' feature to protect sensitive conversations.
- Users can secure locked chats with a four-digit PIN, Face ID, or Touch ID.
- Locked chats are stored in a separate section and have their own memory, distinct from regular chat memory.
- This feature aims to prevent privacy concerns when sharing a device.
- Locking a chat does not create end-to-end encryption or alter data retention policies.
- Resetting the PIN permanently deletes all locked chats.
- The feature is available on most ChatGPT plans, excluding healthcare and temporary/archived/group chats.