Open the Photos app and select the photo
Tap Share
Tap Mail
Choose a smaller image size when prompted
Send the email to yourself or save the attached smaller version
Use the Files app to export the photo in a smaller format if available
Turn on iCloud Photos with Optimize iPhone Storage
Use a Shortcuts automation to resize images before saving
Install a photo compression app from the App Store
Save the photo as JPEG instead of HEIC when exporting if needed
Crop the photo to reduce file size
Reduce the image resolution using an editing app
Use AirDrop or Messages only if the receiving app compresses the image
Avoid sending as original size when sharing
Delete duplicate or unnecessary photos to free storage