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to begin to use a computer system, as by entering a password, etc. (This action may be recorded, or logged, automatically in the computer's memory.) What time did you log on to the system this morning? I always log on before I get my first cup of coffee.
log someone on (to something)
to allow someone to link (electronically) to a computer system. (This action may be recorded, or logged, automatically in the computer's memory.) I will log you on to the system if you forgot how to do it. I will log on Jill, who is late.
log onalso log in
to open a computer system so that it can be used As a graduate student, Erin often logged on to the system from home around midnight. Internet companies are trying to help business travelers log in while they're on the road.
To provide the necessary information to a computer for someone to be allowed to access computer resources: Let me log you on so that you can access the files yourself. You can't use this program until you log on.