Correct spelling, explanation: both log in and login are correct, but they are used in slightly different contexts. Log in is a phrasal verb used when you are referring to the action of entering your username and password to access a computer system, website, or application. In this case, log is a verb, and in is an adverb or preposition indicating the direction or location (into the system or application). Login is a noun that refers to the combination of a username and password used to access a computer system, website, or application. It is the credentials you use to log in.

Definition of log in:
phrasal verb, to connect to a computer system by putting in a particular set of letters or numbers
Before you can access your online banking account, you need to log in with your username and password.
I’ll need to log in to my email account to check for any important messages.

Collocations with log in:
Some most commonly used collocations include:
1. Log in credentials: refers to the username and password or other information required to access an account.
Make sure to keep your log in credentials secure to protect your account.
2. Log in screen/page: the interface or webpage where users enter their credentials to access an account or system.
After opening the app, you’ll see the log in screen where you can enter your details.
3. Log in process: describes the series of steps or actions required to access an account or system.
The log in process is straightforward and only takes a minute.
4. Log in securely: to access an account or system in a way that prioritizes security and protects against unauthorized access.
Always remember to log in securely by using strong passwords and two-factor authentication.

Correct spelling, explanation: the difference between login and log in lies in their grammatical roles and usage. Login is a noun that refers to the credentials used to access a computer system, website, or application. It typically includes a username and password. Log in is a phrasal verb used to describe the action of entering your credentials (username and password) to gain access to a computer system, website, or application. Login and log in are different parts of speech.