Fucking Instagram and their Web interface. Try to get the maximum video size on a horizontal screen. Bonus points when a horizontal video is uploaded to their vertical frame optimised viewer.

I did the math before: it was literally less than 1% of my screen. There's no full screen feature.

Not like it cost them even a measurable amount of money to have one developed. They keep it awful intentionally to get you to install the app. Fuck companies like that.