Login

In computer security, logging in (or logging on, signing in, or signing on) is the process by which an individual gains access to a computer system or program by identifying and authenticating themselves.

Typically, user credentials consist of a username and a password. These credentials themselves are sometimes referred to as a login. Modern secure systems often require a second factor, such as email or SMS confirmation for extra security. Social login allows a user to use an existing cell phone number or user credentials from another email or social networking service to sign in or create an account on a new website.

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

Logging in is usually used to enter a specific page, website, platform or application, 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 when the user takes an action, such as entering an appropriate command or clicking on an external link. It can also be done implicitly, such as by the user powering off their workstation, closing a web browser window, leaving a website, or not refreshing a website within a defined period.

A login page may have a return URL parameter, which specifies where to redirect back after logging in or out. For example, it is returnto= on this site.

In the case of websites 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, thereby making any session handle in the user's cookie store useless.