You emailed yourself some photos from an iPhone and the other end cannot open a single one. That is HEIC. Apple made it the default camera format in 2017 because it stores the same picture in roughly half the space of a JPEG, and almost nothing outside Apple’s own ecosystem followed.
Why Windows in particular struggles
HEIC is a still image wrapped in the HEIF container and compressed with HEVC, the video codec also known as H.265. HEVC is patent-encumbered, and licensing it costs money — which is why Windows ships without the decoder and asks you to install a paid extension from the Microsoft Store to view your own photographs. Android support arrived late and is still uneven. Most web upload forms reject the format outright.
Converting to JPEG makes the problem disappear permanently, because JPEG is the one image format that genuinely works everywhere.
What the conversion costs you
- File size roughly doubles. That is the trade Apple made in the other direction, and there is no way to keep HEIC-level compression in a JPEG.
- HEIC can store 10-bit colour; JPEG is 8-bit. Very smooth skies and studio backdrops can show faint banding as a result.
- Depth maps, Live Photo video and Apple’s editing history are all discarded. Only the still frame survives.
- HDR photographs are tone-mapped down to standard range, so a very bright sky may look flatter than it does on the phone.
Your location data is removed
iPhone photos carry EXIF metadata including the exact GPS coordinates where each shot was taken, along with the date, time and camera settings. Because this conversion rebuilds the image from decoded pixels rather than rewrapping the original file, none of that carries over. For anything you are about to post publicly or send to someone you do not know, that is a meaningful protection rather than a side effect.
Orientation is handled properly, though. Photos taken sideways carry a rotation flag, and it is applied during decoding, so your JPGs come out the right way up rather than lying on their side.
Speed, and why Safari is faster here
Safari and iOS can decode HEIC natively, so on an Apple device the conversion starts immediately. Chrome, Edge and Firefox cannot, so this page falls back to a WebAssembly decoder that downloads once — about 1.4 MB — and is then cached for every subsequent file. On a large batch the first photo is slow and the rest are quick.
All of it runs inside this tab on your own machine. Holiday photographs, pictures of children, documents you photographed rather than scanned — none of it is transmitted anywhere, which is not something an upload-based converter can offer regardless of what its policy says.