YouTube PiP size cannot be manually changed on most devices
Use the device’s picture-in-picture window controls to resize if your device supports it
Drag the PiP window corners or edges to resize on supported Android devices
On iPhone and iPad, PiP size is fixed and cannot be adjusted
On desktop, use the browser’s mini player or window size controls instead
Update the YouTube app and your device OS if resize controls are missing
Check your device settings for picture-in-picture permissions and options