Make all apps use system volume level setup on Android
I sit in a quiet library room and want to see online videos with my smartphone. I turn the volume down with side volume button. But after I open a video App, like YouTube, Bilibili, TikTok, my phone will remember the volume level the last time i used on this App. The sound volume exploded out and everybody looked at me. I'm using Huawei Nova 3 and Android OS 9. I don't know why the App on this phone don't use the system volume level I set for now, or retrieve the last time volume setup. Hope people here can help me.
Keep the phone in silent when you start the app then gradually increase volume. Most applications which may not respect system volume and modify it directly would still respect the silent mode.
You can also use "system volume limiter" apps from play store