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For other uses, see Login (disambiguation).
A screenshot of the English Wikipedia login screen.

In computer security, logging in, (or logging on or signing in or signing on), is the process by which an individual gains access to a computer system by identifying and authenticating themselves. The user credentials are typically some form of "username" and a matching "password",[1] and these credentials themselves are sometimes referred to as a login, (or a logon or a sign in or a sign on).[2][1] In practice, modern secure systems also often require a second factor for extra security.

When access is no longer needed, the user can log out (log off, sign out or sign off).


Finger print login, a recent banking security application.

Logging in is usually used to enter a specific page, which trespassers cannot see. Once the user is logged in, the login token may be used to track what actions the user has taken while connected to the site. Logging out may be performed explicitly by the user taking some actions, such as entering the appropriate command, or clicking a website link labelled as such. It can also be done implicitly, such as by the user powering off his or her workstation, closing a web browser window, leaving a website, or not refreshing a webpage within a defined period.

In the case of web sites that use cookies to track sessions, when the user logs out, session-only cookies from that site will usually be deleted from the user's computer. In addition, the server invalidates any associations with the session, making any session-handle in the user's cookie store useless. This feature comes in handy if the user is using a public computer or a computer that is using a public wireless connection. As a security precaution, one should not rely on implicit means of logging out of a system, especially not on a public computer, instead one should explicitly log out and wait for the confirmation that this request has taken place.

Logging out of a computer when leaving it is a common security practice, preventing unauthorized users from tampering with it. There are also people who choose to have a password-protected screensaver set to activate after some period of inactivity, requiring the user to re-enter his or her login credentials to unlock the screensaver and gain access to the system. There can be different methods of logging in that may be via image, fingerprints, eye scan, password (oral or textual input), etc.


The noun login comes from the verb (to) log in, which was formed by analogy with the verb to clock in. The expressions may also have a more literal origin[citation needed]—computer systems tend to keep a record, called a log, of users' access to the system; hence, to log in is to prompt an entry into the system's log by accessing the system. It was possible to use some early systems such as ITS without logging in.

Signing in connotes the same idea, in that providing the credentials that authenticates a user's right to entry is akin to a signature.[citation needed]

The terms began to enter common usage among computer users with the origin of the computer Bulletin Board System (BBS) in the 1970s.

While there is no agreed difference in meaning between the three terms (login, logon and sign in), different technical communities tend to prefer one or another - Unix, Novell and Linux typically using "login", whereas Microsoft typically prefers "logon".[citation needed]

See also


  1. ^ a b The Linux Information Project, detail and definition of login and logging in.
  2. ^ Oxford Dictionaries, definition of login.