Whether you know it or not, your iPhone and iPad actually tracks what you're doing in Safari for several reasons. The main ones being to speed up browsing and to store logins. On the down side, website data can also be used for tracking purposes. If you'd rather not have sites track you, clearing out this data now and again is a good idea.
Launch the Settings app from the Home screen of your iPhone or iPad.
Scroll down and tap on Safari.
Again, scroll down to the bottom and tap on Advanced.
Now tap on Website Data.
This is where you'll see all the sites storing data via Safari. Scroll to the botom and tap on Remove All Website Data.
You'll be asked to confirm you'd like to delete all data with a detailed explanation of what it does. Just tap Remove Now to confirm.
That's it. All the website data currently stored on your iPhone or iPad is now gone. Depending on how much you browse, you may have noticed lots of data being stored. This is also a way to free up a little storage space now and again if you find yourself running dangerously low.