OnePlus
Change App Icon Shape and Style auf OnePlus
OnePlus lets you swap the shape of every app icon at once through the home screen settings, without touching individual apps. This is handled by the Icon pack option, which applies a uniform contour style (square, circle, teardrop, and others depending on the installed pack) across all app symbols on the home screen and app drawer.
To change it, tap and hold a free area on the home screen, then follow this path:
Tap and hold a free area on home screen ➤ Tap on Home settings ➤ Tap on Icon pack ➤ Choose an Icon pack ➤ Tap on Save
The pre-installed Oxygen and Hydrogen icon packs are always available here without any download. If you want a different shape, additional icon packs can be fetched directly from the same screen before you pick one and save it.
If icons still look unchanged after saving, the home screen may need a manual refresh or a short delay before the new contour is applied everywhere. If only some app icons stay square while others change shape, that specific app usually ships with a fixed icon that ignores third-party icon packs, and no setting in the Icon pack menu will override it.