You don't always need an APK; as YouTube tech guides suggest, you can simply search "speed test" in a mobile browser to get immediate results.
Hidden app traffic consuming bandwidth.
Some APKs provide a live "Speed Indicator" in your status bar, allowing you to see exactly how much data is being transferred while you use other apps. Download Speed apk
Physical distance from a router or cell tower. You don't always need an APK; as YouTube
Throttling by your carrier once a certain limit is reached. You don't always need an APK