Use your phone’s built-in Hide/Lock feature in the Gallery or Photos app
Move photos to a Secure Folder or Private Album if your device has one
Store photos in a hidden folder and exclude that folder from Gallery scanning
Rename the folder with a dot at the beginning on Android to hide it from some gallery apps
Use a file manager to move photos out of the main DCIM or Pictures folders
Turn off cloud sync for private photos if they appear in shared gallery views
Use app lock or folder lock settings to restrict access to the gallery app
Delete photos from the gallery and keep them in a password-protected vault app
On iPhone, use the Hide option in Photos and disable the Hidden album from showing
On Android, use Google Photos archive or locked folder features if available