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What are the preferred use cases for the following sets of terms:

  1. Log in / Log out
  2. Log on / Log off
  3. Sign in / Sign out
  4. Sign on / Sign off

From what I can guess, "Logging in" should be used for a long-lived session (like a website), whereas "Sign in" should be for something that you will be attending to (like IM or a financial transaction).

I'm a little fuzzy here...

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I've always used Login/Logout without the space. I notice that Microsoft is preferential to Sign in/Sign out.

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Login/Logout are nouns. Add the space and they become verbs. – Mark H Sep 19 '10 at 8:35
@Mark H +1 for the eagle eye observation. Most of us couldn't have cared less :) – yati sagade Sep 6 '11 at 19:58
Stack Exchange, Google, Facebook and Twitter, Flickr and Yahoo all use verbs -- with the space. – Hugo Sep 3 '15 at 7:39

These are all a matter of style (I prefer those with in/out over on/off).

Just choose one pair and make sure you use them consistently, and definitely don't mix your terms like Log on / Sign out.

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I forget where I read it, I think it was the Rails company Thoughtbot but the basic idea was to use "Sign" for everything so that there are three actions always:

  1. Sign In
  2. Sign Out
  3. Sign Up

This nomenclature makes sense because the basis for authentication is a logbook, so you "sign in" when you enter and "sign out" when you leave.

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There isn't a "proper use." It's all preference. They're all synonyms, as far as the Web At Large is concerned.

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SO sites goes with Log in and Log out! So it could a standard way!

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They are all similar, occasionally you might even see Enter / Exit or Start / Stop or ...

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Microsoft has very well defined guidlines to this... For anyone w/ Safari, you can follow along in "Framework Design Guidlines - Conventions, Idioms, and Patterns for reusable .Net libraries"

Table 3-2 lists the "Microsofty" way (for what it's worth):

Use Log Off not Log Out

Use Log On not Log In

Use Sign In and Sign Out not Log On and Log Off

There are about 20 conventions listed and they are listed for the sake of consistency...

I always preferred "Sign In" over "Log On", but it's just personal choice to me...

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Which one sounds most natural?

What's your login detail?
What's your logon detail?
What's your sign in detail?
What's your sign on detail?

That's sufficient for me to chose one.

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Do you mean What are instead of What is? – Fosco Sep 6 '11 at 20:06
@Fosco: login detail can be singular if you think of it as a username/password pair, or it can be plural if you think of it as a bunch of authentication information. It doesn't really matter for my main point, though I corrected it anyway. – Lie Ryan Sep 6 '11 at 20:22

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