Do I 'Log Into', 'Login To', or 'Log In To'?

Question

I've been speaking English for a long time but I've only been logging in for a couple of decades and every time I write it I am confused about the proper usage.

Do I log into the system?

or

Do I login to the system?

or

Do I log in to the system?

Answer 1

TL;DR — I would say "Log in to" or "Log into" but not "Login to"

For me, I would say option 2 is definitely 'wrong'. From Wikipedia:

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 by identifying and authenticating themselves. The user credentials are typically some form of username and a matching password, and these credentials themselves are sometimes referred to as a login (or logon, sign-in, sign-on).

So if I see the phrase "login to" I'm thinking of "credentials" (e.g. username/password combo) [noun] [preposition], for example:

Use your login to gain access.

rather than an action:

Use your password to log in to the system

The UK's The Guardian newspaper's Style Guide backs this up somewhat:

• log in, log on, log out, log off

  • verbs

• login, logon

  • nouns (“I’ve forgotten my login/logon”)

But you could argue that given it's in a "Style Guide" shows it's a matter of preference!

Personally, I'd go with option #3 — log in to — as "log in" is a 'phrasal verb' by itself. I see the "in" as being more closely related to "log" than to "to", so it seems odd to phrase it as "into", but it's so common to combine "in" and "to" in English, that I can't really object to #2 either :)

On an appeal to authority...

• Cambridge Dictionary lists "log in to" exclusively
• Merriam Webster gives "log in" as a variant of "log on", but also calls out "often written as log onto and log into

Taking similarly structured 'phrasal verbs' that end in a preposition, a more common one is probably "check in" (as in, "check in to a hotel").

Going back to the Guardian, they similar distinguish between "checkin/checkout [nouns]" vs "'check in' and 'check out' [verbs]" (though they don't call out a distinction between "check in to" vs "check into").

If you look at their usage in the wild, you get 1,510 results for "check in to" and 1,090 results for "check into" — so a reasonably even split.

Answer 2

Dictionaries/style guides may have recommendations, but I don't think native speakers are consistent on this (I sometimes second-guess myself). The Dictionary.com Usage Note acknowledges that the spelling "login" is often used for the verb even though some disapprove of it.

Answer 3

To be correct technically, the proper usage is "login to" here. The word "login" is associated with the process of authenticating with (usually) a username and password to a computer system.

The phrase "log into" doesn't really have a clear meaning in this context although it is frequently misused in this way. Computer systems "log" data or events and they may "log into" a file but users don't "log into" them.