Possible Duplicates:
Logging in or on?
UI Terminology: Logon vs Login on Stack Overflow

On Windows computers, the terminology log on/off is used. In SE and on many sites, log in/out is used.

Are they both correct and equally appropriate for any situation, or are there differences?

If they are exactly synonymous, which is standard?

  • @MrHen: I respectfully beg to differ. The title of that question is deceptive. It does not address in vs. on.
    – Daniel
    Jul 12, 2011 at 14:56
  • @drm65: The answer to that question links to another SO question that does address the issue.
    – psmears
    Jul 12, 2011 at 16:20

3 Answers 3


This is what the NOAD reports:

Log in (or on) go through the procedures to begin use of a computer system, which includes establishing the identity of the user.
Log off (or out) go through the procedures to conclude use of a computer system.

Same on the OALD, this means they are synonyms. If you check on Wikipedia, they are given as corresponding expressions, too.

  • 4
    To clarify, one "logs on" and "logs off" a system, a computer. One "logs in" and "logs out" of an application, website, etc. There may be exceptions, but in general the first is more hardware-centric, the latter software based.
    – The Raven
    Jul 12, 2011 at 13:48
  • I kind of thought the same, but you see them used pretty much interchangeably...
    – Alenanno
    Jul 12, 2011 at 13:50
  • I don't recognise the distinction @The Raven is making. I recall many years ago when I changed jobs or activities and so changed from one make of computer to another that "login" was replaced by "logon" or vice versa (I don't even remember which way round it was).
    – Colin Fine
    Jul 12, 2011 at 13:58

6 of one, half a dozen of the other. The computer, because it does so many different things for many different people, and because applications of that computer abstract all the nitty-gritty hardware from the "user experience", is thought of in many different metaphorical or analagous contexts. These various analogies we use to describe computers call for differing prepositions when describing the tasks, and sometimes two prepositions, coined in the context of a particular computer analogy, become commonly used.

Personally, I think "log in/out" is the better term. This is because I think of the computer as a part of the networked IT system, and when I enter my username and password, the action of me beginning work is "logged in" to the computer and the system behind it. I think of it similar to if I punched a time clock every day, and "clocked in" and "clocked out".

However, "log on and log off" could have similar analagous meaning to someone: the terms "sign on" and "sign off" have been common in radio and television for decades before the personal computer entered the scene, and in the context of going "on air" vs "off air", or "on duty" vs "off duty", these acts would translate to the computer pretty seamlessly.

There are many other terms used. For instance, I see "sign in" and "sign out" a lot in websites; GMail and the BofA website use these terms to refer to their security session management. This sounds just as logical as "logging in/out" to me.


They seem to be synonymous and from my experience they definitely are.

In computer security, a login or logon (also called logging in or on and signing in or on) is the process by which individual access to a computer system is controlled by identifying and authentifying the user referring to credentials presented by the user.

A user can log in to a system to obtain access and can then log out or log off (perform a logout / logoff) when the access is no longer needed. To log out is to close off one's access to a computer system after having previously logged in.


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