iPhone photos use HEIC. Convert to JPG for universal compatibility.
iPhones save photos in HEIC (High Efficiency Image Container) by default. HEIC produces smaller files than JPEG with similar quality, but many websites, email clients, and older software do not support it. When you need to upload a photo somewhere or share it with someone on Windows or Android, converting HEIC to JPG ensures compatibility.
Apple adopted HEIC to save storage. A HEIC file can be 50% smaller than an equivalent JPEG. On devices with limited space, that matters. The format also supports multiple images (e.g., Live Photos) in one file. The tradeoff is compatibility—outside the Apple ecosystem, HEIC support is still limited.
Convert to JPG when uploading to websites that don't accept HEIC, when emailing photos to people who might not have HEIC support, when editing in software that only reads JPEG, or when archiving in a format that will work everywhere for years to come.