You decide what goes in
Four ways information gets in
What you type, what you upload, what the tool remembers between chats, and what connected tools let it reach, such as your email, calendar or cloud files. The first two are obvious; the last two are easy to forget. Memory features and app connections are useful, but each one widens what the assistant can see, so switch on only the ones you actually need.
Keep these out by default
Passwords and security codes (no legitimate assistant needs them), bank and card numbers, ID and passport numbers, other people's private details, health records you would not want stored, and confidential work material your employer has not approved for AI use. If an assistant or an app claiming to be one asks for a password or code, stop: that is a scam pattern, not a feature.
Check the settings once
Most major assistants let you turn off use of your chats for training, delete history, use a temporary or private chat mode, and manage memory. Work and education plans often have stricter defaults than free personal accounts. Spend five minutes in the settings of the tools you use; it is the single biggest privacy improvement most people can make.
Three questions before you paste
Does the task actually need this detail? Would I be comfortable if it were stored? Is it mine to share? Often you can remove names and numbers and still get a good answer: "my colleague" instead of a name, "£X" instead of a real salary. For anything you are unsure about, leave it out first and add detail only if the answer is not good enough without it.
Have you ever pasted something into an AI tool and wondered afterwards where it went?