Forgive me but I have been thru all of the docs…
This is a question often asked by users who are prompted to download the Unity web player to play a game, not developers.
How much disk space does the Unity web player require?
…I know it captures about 5 to 130 Mg RAM when running.
Chrome grabs about 90Mg of disk space due to all the compatibility stuff it includes.
A stripped down version is slightly under 36Mg (most users will not go thru that trouble…)
and it runs on about 42Mg and up depending on how many TABs are opened.