Best file format/ settings for alpha channels?

iadagraca

Is there a universal standard for alpha channels? I'm having an issue where an alpha channel file causes issues in the programs i've used like sketch fab and blender.

I'm fairly new to game characters and i know it doesn't matter for cg renders.

So i need to know the best way to save black and white alpha files.

I don't know if i'm painting them wrong in photoshop or what.