How and where is it better to store the code for a while?

Question

PHP

I am writing a website related to HTML and CSS lessons. Lessons have tasks to complete.
Problem : the written code will disappear after reloading the page.
Question: how best to autosave the code and where to store all this code?
I'm going to keep the code for a day, more is not needed. I have only three options for where to store, maybe you can suggest something else. The first option is to store in cookies, the second option in the database, the third in files. The first option is in the database: here the question arises, is the load on the database too heavy? After all, overwriting can be very multiple over a short period of time. It will be necessary to send data by Ajax, there are no problems with this. With cookies, I think it's easier and more efficient, maybe I'm wrong, but so far there are no thoughts on how to put code into cookies. And the last option is to store in files, while there are only problems with how to delete them later in a day, of course, there are thoughts.
A little about the system: The code is in the textarea in a certain form (spaces, tabs and hyphens are replaced by the escape sequences \n, \t), in short, all the manipulations will need to be done with the textarea and without reloading the page.
I hope to get your opinion on where it is more profitable to store.

Answer 1

localStorage maybe?

Answer 2

sessionStorage, When the page is closed, the data should disappear?