A little detail that I’ve always taken for granted is the term that is used to invite a person to log in or sign in to a system – that is, to provide their username and password for authentication. I usually just default to the term “log in”, which is what Mac OS X and most UNIXs call it.

It really doesn’t seem like a big detail, except that today I found myself scratching my head thinking “what do my users think when they see ‘log in’?” If you really sit there and think about it, the term “log in” doesn’t make any sense at all. It makes me think of wood – what am I putting the log into, anyway? But on the other hand, “sign in” seems awkward too, if you think about it long enough. So lets look at the alternatives.

Log in and log out, as far as I can tell, are derived from the idea that one would write your name down in a logbook for an important activity. “Login” can also be used as a noun, as in “provide your login and password”, and as an adjective, as in “give me your login information and nobody gets hurt”. It seems like a pretty natural thing to say, but that could be because of all the times I’ve “logged in” to Mac OS X. You can still say “provide your signin information”, but that seems pretty awkward. So “logging in” seems more versatile than “signing in”.

Sign in and sign out seem to have a slightly more friendly feel. Many websites end up using these over login/out. Saying “sign in” feels like signing a guest book, where “log in” feels like registering oneself for some important activity. Sign in and sign out also have the benefit of historical usage. People who remember listening to the radio (remember radio?) would recognize the familiar “this is So-and-So, signing off”.

What do you think?

• Log in/Log out
• Log on/Log off
• Sign in/Sign out
• Sign on/Sign off

Some posts that I found helpful:

• Eric Bowen’s .NET Technology Blog
• Fog Creek Software
• Redneck Definitions