Samsung
Restore Default App Icons auf Samsung
Custom icon packs on Samsung phones are managed by the Galaxy Themes app, not by the individual apps themselves. Once you apply a pack, every app icon on your home screen and in the app drawer gets swapped for a matching graphic from that pack. Because the change sits inside the Themes system, there is no reset switch hidden in Settings ➔ Apps or in the launcher settings.
To bring the stock icons back, open Settings ➔ Themes, then open the Menu and tap My stuff. Select Icons, choose Default, and confirm with Apply. Samsung reapplies its original icon graphics across the entire device in one pass.
This action resets all icons at once. It does not target a single app, so if only one icon looks off, the fix still restores the full default set rather than fixing one entry. If icons look blank or frozen instead of simply changed, that is usually a caching issue with the launcher and needs a separate cache clear rather than a theme reset.
Downloaded icon packs stay installed after this reset. Applying Default only changes what is currently active, so you can switch back to the custom pack later through the same My stuff ➔ Icons screen.