How do i send data over http without it failing due to 4mb of string data

I am working on a data transfer system where anyone can bring his save files over multiple games.
Its working with short strings, but once i try sending over some actual game data worth of 200k characters in string, this error pops up:
image

How do i transfer a lot of string data without the call failing on me?

Is that really all the info you get?

If the issue is actually the length of the data, try sending it in smaller pieces with several http requests.

Is the data compressed at all?

I have sent ‘{“a”,“b”,“c”}’ before and that was detected perfectly fine.