iPhone HEIC and compatibility
Since 2017, the iPhone has saved photos as HEIC by default instead of JPEG, a format that is far more compact for the same visual quality, but that most browsers cannot open without a plugin. Converting to JPG solves the compatibility problem, except the simplest conversion path (drawing the photo onto a canvas and re-exporting) wipes out all metadata in the process, including the date the photo was taken.
The "keep EXIF" option is on by default, and only has an effect when the chosen output is JPEG.
Metadata re-injection is only implemented for the JPEG APP1 segment, not for the PNG eXIf chunk.
The cap exists because the WASM decoder materializes the entire RGBA bitmap in memory, and an oversized file freezes the tab.
Since iOS 11, the iPhone saves photos as HEIC (High Efficiency Image Container) by default, because the format halves file sizes while keeping quality. You can switch to JPEG in Settings › Camera › Formats, but older photos stay HEIC.
Because HEIC, based on the HEIF standard and HEVC compression, stores the same visual quality in roughly half the space of an equivalent JPEG, saving storage and data when syncing to the cloud. Apple adopted this format as the default starting with iOS 11, in 2017.
Because no browser decodes HEIC natively; opening this format requires a dedicated decoder (in this tool, via WebAssembly), and most sites simply do not implement that extra support, so the file shows up as unrecognized.
No, as long as the chosen output is JPEG and the keep-EXIF option is on (the default): the converter reads the EXIF block from inside the original HEIC container and re-inserts it into the output JPEG, preserving the date, camera model, and GPS.
Yes, 50 MB per file. The decoder runs in WebAssembly and needs to materialize the whole uncompressed image in browser memory, and a burst-shot or ProRAW file above that cap would risk freezing the tab before finishing.
Copies date, camera and GPS from the HEIC into the JPG. Orientation is normalized so photos never come out rotated.
HEIC decoding happens entirely in your browser with WebAssembly. No photo is sent to any server.