You decide to store data in the user's browser in order to reduce the amount of data that must be downloaded. What is this process called

client-side storage

Explanation:

The process of doing this is known as client-side storage. Like the name suggests this saves data that is sent to the user's computer on that computer either as cookies or cached data. This data is then used every time that the user decides to enter the same website or access the same program from the browser. Doing this allows these websites and programs to load much faster the more times that the user decides to enter them.