Question Save file in Application.persistentDataPath

I can't understand how saving files with WebGl works.
I need to save a .gif image generated during the program execution.
In editor it works, but not on web.
If I understand correctly Application.persistentDataPath is a kind of playerPref in WebGL and only saves key-value pairs.
I would like to save the file, on a folder on the server, not on the user's hd.

This is the indexDB after saving on my server.

 

My files appear to be saved.
How can I check that everything is ok?



If I try to open the file directly it won't find it.



I now have a key-value . So I have to rebuild the gif file from the value string?