Fit game to android to android screen in HTML5

I designed a game and exported in HTML5, but when I open it on mobile it doesn’t occupy the whole screen. what can i do about this any ideas?

Did you choose fullscreen?
Can you give more details about what you see, or a screenshot?

yes, i chose fullscreen, but there is still purple part showing when i open the game in browser be it laptop or mobile.

Purple is the background color of your scene?
Try tweaking the resolution settings, see what happens.