HEIC Format
The iPhone’s default photo format — compact, but not supported everywhere.
What is HEIC?
HEIC (High Efficiency Image Container) stores photos using the HEVC codec. iPhones and iPads use it by default because it takes about half the space of JPG.
Why HEIC causes problems
Many Windows apps, Android devices, websites and upload forms cannot open HEIC. Converting to JPG makes your photos work everywhere.
How to avoid HEIC on iPhone
On iPhone go to Settings → Camera → Formats and choose “Most Compatible” to save new photos as JPG. For existing photos, convert them with PhotoTools.