Can I skip some variables in boost serialization?

I have Players class and it has some variables

class Players
{
private:
    friend class boost::serialization::access;
    template <class Ar>
    void serialize(Ar &ar, unsigned)
    {
        ar &username &password;
    }

public:
    std::string username = "", password = "", email = "";
};

I just want to serialize username and password. I dont want to add email too. I'm getting error after trying to deserialize it.

Your code seems correct. Remember that you cannot deserialize an archive that you created with an old version of the serialization routines.

If that is the case, as a very primitive workaround you can do this below, or learn how to deal with archive versions.

    template <class Ar>
    void serialize(Ar &ar, unsigned)
    {
        std::string dummy_email = "";
        ar &username &password & dummy_email;
    }