I noticed Fender's online guitar tuner page keeps the sound of the string playing even after you leave your browser on your phone. For example, if I'm messing with the tuner and then decide to switch apps to go into Reddit for a bit, the sound does not get cut off and just continues.

Furthermore, their sounds keep working even when you come back to the browser without a manual refresh of the page.

Link to Fender's guitar tuner: Fender Guitar Tuner

Does anyone know how Fender is doing this? I've seen some sites including, my own, where the sound gets cut off if you switch apps on your phone. I also noticed that they are using react for this.