OnePlus
Enable Developer Options auf OnePlus
Developer options are hidden in OxygenOS by default because most of the switches inside are meant for app testing, not daily use. For a typical user, only a handful of entries matter, and USB debugging is the most requested one, since it lets a computer send commands directly to the phone over USB.
To reveal the menu, open Settings and go to About phone. Tap seven times on Build number until a counter appears near the bottom of the screen.
After the last tap, the phone asks you to confirm your identity. Enter the current pattern, PIN or password when prompted, then watch for the pop-up that confirms Developer options are unlocked.
The new menu now appears one level up, usually near the bottom of the main Settings list or inside System, depending on your OxygenOS layout. From there you can turn on USB debugging or adjust animation speed and other developer-focused settings.
Leave switches you do not recognize untouched. Some options affect battery behavior or app stability, and resetting them later means repeating the unlock steps again.