As I said in the title, I am wondering what is the meaning of the following expressions, and what are the differences between them ?

  • "Sign up"
  • "Sign in"
  • "Log in"

4 Answers 4


While Hellion describes those terms in general, I am writing here in the context of the cyberworld that also includes the gadgets. You mentioned log-in and that's what makes me think that you probably want to know the difference in the context of Internet.

Well, sign up simply means to register. It could be portal, newsletter or things the like. So when you visit and access anything for the first time, you need to sign up. Often, this is referred to as register. For instance, if you are new to Twitter, you need to sign up first.

What is interesting is sign in and log in. Well, both mean same that you enter somewhere where you are already registered. The web portals use both the terms. Facebook, ELL and COCA calls it Log in, whereas Google, Twitter, Bank of America and LinkedIn uses Sign in.

Note that all these portals uses sign up for the process of first time registration and not log up.

A subtle difference

I'm acquainted with webmastership as well and it's interesting to know that during our audit, we check the log. The 'Log' includes the number of sessions per user. The session is a complete cycle of the user logging in and then after the work is done, logging out..

This means that if you are signing in for one session, the correct word is log in. So, for the user, it could be sign in but for the system, it's log in.

It is for this reason, content management software/portal like WordPress uses log in because it maintains the log each time you sign in and sign out which will complete the cycle of one session. It is for this reason again, the computer asks to log in and not sign in. After all, you enter and come out completing one cycle i.e. session.

What I prefer is asking the user to log in if you are strictly maintaining the record (--say WordPress or Bank portal) and in other case where maintaining log is not so important (say a subscription for the newsletter, jokes, pranks or the like) sign in.

While using these words, it's important that you stick to one style. If you ask the user to log in, give them an option of log out and not sign out and vice versa.

Not exactly the answer but important to mention.

Log on or Log in - You log on to the URL/Website and it'll take you on the webpage as a guest or non-registered member. You log in and the site is personalized for you. For instance, log on to Amazon.com and you see all the products listed. You are just a visitor. Log in to Amazon.com and you see all the products listed along with your personalized Amazon that may have the history of your purchase, favorite items and other services that Amazon provides to its registered user.

Good question BTW. +1

  • 1
    @TrevörAnneDenise It's our pleasure. I had a great debate on this topic during my session in my company. Thanks for providing me an opportunity to recall everything I said then. Haha... But remember, Hellion's approach (out of the Internet context is useful.)
    – Maulik V
    May 29, 2014 at 11:42
  • I'm pretty sure about this answer. Downvoters, I defy you! :)
    – Maulik V
    May 30, 2014 at 4:30
  • 1
    It's very good. I am especially impressed that you consistently remder those phrasal verbs as separate words. Running them together ( "login") is rampant, particularly among computer/network people, many of whom apparently conflate the verb usage with the noun or adjectival usage, thinking that they have to use the same rendering for all usages! Apr 3, 2015 at 8:30
  • You're probably getting downvoted due to your claim that "Log In" has something to do with the concept of a session. On this point, you speak objectively, without external references of any kind. I believe most UI professionals would put your perspective about sessions solidly in the "opinion" category.
    – rinogo
    Nov 22, 2019 at 2:31
  • I see a lot of thoughts and ideas have gone into this post. But some of the ideas and points are not well articulated and thought through, such as the argument about sessions. To tell you the truth, I'm not quite sure what the argument really is here. Yes, I do think that the idea of a login session, i.e. the duration of a login, can and should be brought into the discussion if you want to broaden the topic. But you have to elaborate on that. The simple fact is that without a "log in" there is no "log out". Nothing without a start has an end. "Session" is simply duration, a passage of time.
    – Samir
    Aug 22, 2022 at 19:18

To Sign up (for something) is essentially to enroll in it: you formally register your intent to participate. Generally this happens well in advance of the actual start date.

You sign in to a place to officially record your presence there. At a school, for instance, all visitors might be required to sign in at the office (generally by writing their name, purpose, and time of arrival in a designated book) and later sign out (by putting their time of departure on the same line) so that the school officials know at all times who is on the premises besides the teachers and students.

In modern usage, you log in to a computing system so that the system can present you with the options and information that you are entitled to use and view. As with "signing in", it is primarily a security measure, but it is always referring to an electronic system.

(In older usage, logging in was basically the same as signing in.)

  • 3
    "Sign up" is also known as "register". It's generally a one-time thing. For computing systems, "Sign in" = "Log in", where you usually give a user ID and password (established during Signup). N.B.: "Sign up", "Sign in", and "Log in" are verbs (action), and "Signup", "Sign-in", and "Login" are nouns (objects).
    – Phil Perry
    May 28, 2014 at 18:39
  • 3
    "Sign in" and "Log in" are synonymous and still used interchangeably today when dealing with computer systems (websites, databases, user accounts, etc).
    – Doc
    May 28, 2014 at 20:12

Sign up means "to register; to create an account".

In computing, sign in and log in are synonyms. Both mean "to open a session with an account that is already created". There is one difference: the derived noun login "a username; a session under that username" exists, but there is no such noun as *signin.

Outside computing, sign in and sign out are the usual terms. You "sign in" when you sign your name on a sheet to indicate you've arrived at a place, and you "sign out" when you sign your name to indicate that you're leaving.

In many places, you sign in but not out, because there's no reason to keep track of who's leaving. For example, you might sign in at the hospital to let them know you've arrived, then sit down and wait for your name to be called. But there's often no need to sign out.

  • Sign in happens when you enter username and password into a site to access the pages that are restricted. This is also referred to as membership.
  • Log in is successful when your credentials (i.e username and password) match with what is already stored in database. This is called authentication.

For example, if you're booking online tickets you need to log in, otherwise the system won't know who is booking them.


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