Key Difference: Login refers to the credentials that are required in order to gain an access, whereas log on refers to the process to visit or access computer, database or system. Generally, log on is used for systems that do not require user credentials. However in operating systems like Windows, log on is used to describe the act of gaining access by using username and passwords.

In the modern era, most of the work is based on computers and especially on internet. User credentials are therefore very important in terms of security as well as for providing a customized personal functionality in terms of access. Many people confuse terms like log on, log in, login, etc. Therefore, it is necessary to bring out the differences between them.

Login defines an activity through which one can get access to various websites, as well as create an account. It identifies and authenticates the user through the credentials presented by the user. Generally, a login requires a user name and a password. It may also require an e-mail ID or a password. Passwords are important and thus should be kept confidential.

For example, you create a facebook account by signing up for the first time. Now once your account is created, next time when you visit the website you just need to click on the Log in button and provide the same credentials as defined during the time of signing up.

Therefore we can describe it as the act of logging into a computer, system or database. it is used as a noun.

For example:

If you know the password you can login into the system.

Login activity failed due to a power failure

Login attempts must be minimized.

Log on describes a phrasal verb referring to go through the procedures to begin use of a computer, database or system. It means to visit especially in context to a website. A person logs on to a website, if he visits it. A person does not require providing login details to visit or open all the websites. However, in windows, log on refers to the act of signing in by entering a username and password. 

For example:-

Just log on to find out the services offered by our company

Log on to my new website

How can I log on windows, in case I do not remember my password?

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