About HEIC to PNG
PNG is the right target when you intend to edit the photo afterwards, or when whatever you are feeding it to insists on PNG. It is the wrong target if you simply want a file that opens everywhere — JPG does that at a fraction of the size.
Expect a very large file. This is the part worth setting expectations on. HEIC is one of the most efficient image formats in use; PNG is lossless and cannot discard anything. A 2 MB iPhone photo commonly becomes a 20 MB PNG or larger. Nothing has gone wrong — you have converted from one of the most efficient formats to one of the least, which is exactly what lossless means for photographic content.
If that surprises you, JPG is almost certainly what you actually wanted.
When PNG genuinely is right. If the photo is about to go through several rounds of editing and saving, converting to PNG first freezes the quality: every subsequent save is lossless, where a JPG would degrade a little each time. If a design tool, print workflow or API requires PNG, you have no choice. And if you need an alpha channel to work with, PNG gives you one — though you cannot recover transparency a photograph never had.
Decoded on your device. Browsers ship no HEIC decoder, so nearly every converter for this format uploads your photo to a server that has one. We ship a WebAssembly build of libheif instead, so the image is decoded on your own machine. That matters here because HEIC files are camera roll — and iPhone EXIF routinely carries GPS coordinates accurate to a few metres.
EXIF is not preserved. The image is decoded to pixels and re-encoded, so camera settings, timestamps and location do not survive. For photos being shared publicly that is usually a feature; if you need the metadata kept, use something that preserves it.
The WebP option is offered alongside PNG because it is lossless too when quality is maxed, and substantially smaller. Unless something specifically demands PNG, it is the better choice.
Questions
Why is the PNG so much bigger than the HEIC?
HEIC compresses extremely efficiently; PNG is lossless and cannot discard anything. Ten times larger is normal. If size matters, convert to JPG instead.
Is my photo uploaded?
No. We ship a WebAssembly HEIC decoder, so the photo is decoded in your browser. Most converters for this format upload, because browsers cannot decode HEIC natively.
When should I choose PNG over JPG?
When you are about to edit repeatedly and want no further loss, or when software specifically requires PNG. Otherwise JPG is smaller and opens everywhere.
Is GPS and camera data kept?
No. The image is re-encoded from pixels, so EXIF including location is dropped.