Be on to someone.


Senior Member
Hey guys,

There's this phrase "I'm onto you." Does this mean that I've figured you out or made some discovery about you?

  • Packard

    Senior Member
    USA, English
    When someone is on to you it means they know what you are up to.

    When someone is up to something it generally is in reference to some activity that would be frowned upon.

    When you are on to someone you know what they are up to. That is you are aware of some sort of unsavory behavior or planned behavior.


    Senior Member
    Hi, everyone. I want to make sure the meaning of the phrase "to be on to someone". Do it mean that we've already discovered what someone has done, or we are watching him/her and we will discover what he/she has done? Thanks.

    The following is the sentence that I saw, and it does not have a context.
    "My supervisor is onto the new saleswoman who is taking money from her sales register."


    Senior Member
    << ------ >>

    Just to be clear, it means that somebody is aware that another person is doing something that he shouldn't be doing. "I'm onto you" = "I know that you are up to no good".
    Last edited by a moderator:


    English - England
    Hi EnglishBug,

    I'd say that the phrase shows that the woman has already been found out and will soon be confronted about it.


    Senior Member
    Cantonese, Hong Kong
    If the police are on to a criminal, does it necessarily mean the police are having a general picture of what the criminal is up to, but they still need a bit more investigation to be 100% sure what he is doing?