Gclid
The long form is the Google Click ID, a small string of numbers and letters that is used as a unique identifier for website visitors.
It stands for Google Click IDentifier. It is a small string of numbers and letters that serves as a unique identifier for website visitors. This is usually used to track individual users when they click on pay-per-click ads so that their interaction with a website (whether converted, on which page and by what method) can be tracked and attributed to Google. †
