how to keep games running when not in focus?

some games will run fine when i like alt tab to discord or swap tabs to youtube. but others will just stop working. is there any fix or like way to force it to work while the tab is not in focus? i use firefox

Browsers will not throttle a tab if it's playing audio so you can make a JS hack to play an empty sound effect on a loop if you want a specific browser tab to not throttle.

You can also disable browser-wide throttling by changing some of the options in about:config, but that's not recommended since it can slow down your browser: https://wiki.melvoridle.com/w/Mitigating_Browser_Throttling#Firefox

some games works by having it oppen in a new window instead of tab