my server side changed from http to https yesterday,
and since that change, I always get '400 bad input' from the server.
note that both iOS version and me trying in POSTMAN works just fine.
but on android version i get 400 errors.
after exploring and diving into it for a few hours I discovered that if I don't send any headers my request is GOOD!

well, 400 says bad input, meaning I'm not sending something correctly,
but after trying many kind of headers and playing with it, nothing works..
only empty headers pass.

while he does, you said you never used Volley..
what do you recommend using then?
I'm kinda new to android and never used anything other than volley with rest api

well, moving to Ion is a viable option if it can support my customizable HTTP headers,
it's a lot of work tho since i already have my whole app based on volley with 40-50 server calls.
it's all well written and organised in one class, but still it's a lot of writing.

well, I know what you're saying Mark.
weird thing is that on our testing server which is still on http everything works normally.
but on the https it's going bad, and I'm not changing even one line of code

Got it.
i'll have a little sit down with my server guy then and try to work it out,
because until now he told me "it's working on iOS, it's not a server problem".

apparently I found the problem, for some reason volley with https is reacting differently in the headers.
the charset=utf8 doesn't work, but charset=utf-8 does work!

the " - " makes that difference.
so it's solved, just wanted to say thanks again !