Most people converting an iPhone HEIC photo want JPG — it’s universally compatible and reasonably sized. PNG is the less common but sometimes more correct choice, and it comes up specifically when you’re planning to do something further with the image rather than just view or share it as-is.
The case for converting to PNG instead of JPG
HEIC, like JPG, is a lossy format — some image detail is discarded during compression in exchange for a smaller file, in a way that can’t be perfectly recovered. If your plan for a photo is a single conversion and then you’re done with it, that’s a non-issue. But if you’re about to open the photo in an editor and make several rounds of changes, each with its own export step, converting to a lossy format first and then repeatedly re-saving it compounds quality loss with every pass. Converting to a lossless format like PNG as your working copy avoids that — the conversion from HEIC to PNG still involves one lossy-to-lossless step (HEIC’s own original compression can’t be undone), but everything you do to the PNG afterward stays lossless until you export to a lossy format again at the end.
PNG also matters if your editing plans involve transparency — removing a background, compositing onto another image, building a sticker or cutout. JPG has no concept of transparent pixels at all; PNG does, via its alpha channel. The HEIC photo itself won’t have transparency (a camera photo is always a fully opaque rectangle), but if you’re about to add it, starting from a format that supports it makes the rest of your workflow smoother.
What you’re trading for that flexibility
PNG’s losslessness isn’t free — it comes at the cost of file size. A typical photo converted to PNG can easily be five to ten times larger than the same photo converted to JPG at a quality setting most people couldn’t tell apart from the original. For storage, email attachments, or web use, that size difference matters a lot; for a working file you’re about to edit and then export from again in your final format, it’s a reasonable, temporary cost.
The actual conversion process
Whether you’re converting to JPG or PNG, the underlying first step is identical: the tool has to decode the HEIC file’s compressed data into raw pixel information, since nothing outside Apple’s ecosystem can read HEIC’s compressed format directly. From that point, the only difference is which encoder the pixel data gets handed to afterward — JPG’s lossy encoder, which throws away some detail to shrink the file further, or PNG’s lossless encoder, which preserves every pixel exactly as decoded. Choosing PNG here means you get back precisely the pixel data the decoder produced from your HEIC file, with no additional compression-related changes layered on top.
A quick gut check before choosing PNG
If you’re not sure which you need: ask whether you’re about to edit the image further, need transparency, or are archiving something where pixel-perfect fidelity actually matters (a scanned document, fine art reproduction, anything where compression artefacts would be a real problem). If none of those apply — you just want to view it, attach it to an email, or upload it somewhere — JPG is almost always the better default, both for file size and because it’s what most software and forms expect to receive.