JPEG → PNG · runs on your device
JPG to PNG, so further edits cost nothing
Every time a JPEG is saved it loses a little more detail. Converting to PNG stops that, which is what you want before an image goes into a tool that will save it again and again.
A JPEG that has been opened, cropped and saved half a dozen times looks measurably worse than the original, because each save re-applies lossy compression to an already compressed image. The damage accumulates and cannot be undone. Converting to PNG before editing freezes the picture where it is: PNG stores exactly the pixels it is given, so no amount of saving degrades it further.
To be clear about what this does and does not do: converting to PNG cannot recover detail the JPEG has already discarded. Compression artefacts in the original are preserved perfectly, along with everything else. The point is to stop further loss, not to repair past loss.
PNG also carries an alpha channel, so an image converted here can have its background made transparent in an editor afterwards, which a JPEG can never do. Expect the file to grow substantially, particularly for photographs.
Questions
- Will converting to PNG improve the image?
- No. It prevents further loss but cannot restore detail the JPEG already threw away. Existing compression artefacts are preserved exactly.
- Why did my file get so much bigger?
- PNG stores everything without discarding anything. For photographs it is commonly five to ten times the size of the JPEG it came from.
- Does this add transparency?
- It makes transparency possible. The converted image is fully opaque, but PNG supports an alpha channel, so you can erase a background in an editor afterwards.
- Is PNG the right choice for the web?
- Usually not, for photographs. WebP gives you lossless quality at a fraction of the size and is supported by every current browser.