A user commenting on the web page of the definition of log in on merriam-webster.com wants to know how to write log in to.
I’m writing step-step [sic] instructions and don’t know whether to say “log in to the website” or “log into the website”. I’m inclined to say the first is correct but my colleague is pushing for the second.
We see three forms of the verb to log in in use online these days.
login to |log in to| log into
The correct form of the verb is log in with the option to add to. To answer the question on merriam-webster.com, one would write in step-by-step instructions “log in to the website.” If you want to skip the rest of this article, just remember to separate the three words when you’re telling a user to log in to a website or sign on to a system or other such instructions when in the context of software.
Log in
Log in is a two-part verb, and so are a host of other terms we see related to software. These two-part verbs consist of a verb plus a particle.
verb + particle
log in|log out|log on|log off
sign in|sign out|sign on|sign off|sign up
opt in | opt out
On a website, these verbs are what we should use when we are calling a user to action. Because a button is a call to action, the button label should be the two-word command form of the verb (e.g., log in, sign in, sign up) instead of the one-word noun form (e.g., login, signup). Text links are often used to call users to action as well, so text links in navigation that are beckoning a user to do something should use the command form too.
Why not log into?
We have the option of adding, to a two-part verb, a prepositional phrase (e.g., to the website) telling a user what to log in to, what to sign out of, or what to opt in to.
verb + particle + prepositional phrase
We should not combine a verb particle and a preposition into one word. Log into is incorrect.
It’s understandable why we have a tendency to combine the particle in and the preposition to making the phrase log into. It looks correct, but the meaning of the phrase has changed. The verb log in has changed to log (to cut down trees or make an entry in a log), which isn’t the meaning we want in the context of software. I doubt any person would actually interpret log into a website to mean to cut down trees into a website (because it’s nonsensical), but that’s the technical reason why log into is grammatically incorrect in the context of software. (In case you’re wondering, we could get a sensible sentence out of log into if we said something like don’t log into that grove of ancient trees).
It’s happenstance that combining in and to into one word (into) still makes sense. If we combine the particle and the preposition in a different two-part verb (e.g., log outof the website), the combination doesn’t make sense.
Why not login to?
The words login and log-in are nouns and can be used as adjectives too, so in the context of software, there will be cases where it’s okay to use these words (e.g., What’s your login to get into the CMS?). But don’t use nouns as calls to action.
I’d like to say that login is the noun and log-in is the adjective so it’s easy to remember, but because online dictionaries don’t agree on a scheme, I think it’s okay to use them interchangeably. You could use either word as a noun and either word as an adjective.
Dictionary.com makes it easy to see that login isn’t a verb.
You cannot say you have loginned, and you are never in the process of loginning. Moreover, you cannot even ask someone to login you; you must ask that person to log you in.
In summary, remember to separate the three words when you’re telling a user to log in to a website or to sign on to a system.
—Dara
P.S. For any verb that is a two-part verb, you would capitalize the particle if that verb appeared in a headline or title where you were capitalizing in title case.
When in, out, on, up, and off (and other words) are serving as particles in a two-part verb, they do get capitalized in title case (e.g., Log In to See Your Personalized Results).
When in, out, on, up, and off (and other words) are serving as prepositions, they do not get capitalized in title case (e.g., Stand in Line to Get It First).
