JPG to PNG re-encodes your JPEG photos as PNG files using a lossless compression scheme, meaning every pixel value in the decoded image is preserved exactly rather than approximated the way JPEG's compression algorithm does. JPEG achieves its small file sizes by discarding information the human eye is less sensitive to — subtle color gradients get simplified, and sharp edges (text, logos, hard lines) develop a faint blocky "ringing" around them at higher compression levels. That trade-off is fine for a photo of a sunset; it's a real problem for a screenshot full of text, a logo with crisp edges, or any image you plan to edit further, since JPEG artifacts compound with every re-save. PNG uses DEFLATE compression instead, which is completely lossless — it can't shrink a photo as aggressively as JPEG can, but it never throws away pixel data to get there.
The format also matters for what happens next to the image. PNG supports an alpha (transparency) channel, which JPEG has no mechanism for at all. Design tools, background-removal tools, and anything that composites an image over other content generally expect PNG input for exactly this reason. Converting a JPEG to PNG doesn't retroactively add transparency — a JPEG never had any to begin with, so the output starts fully opaque — but it does put the file into the correct container format so a background-removal step, layering in a design tool, or export from an editor can add and preserve transparency afterward, which a JPEG output could never hold onto.
This conversion runs in the reverse direction most people expect: PNG to JPG is the common move for shrinking file size before uploading a photo somewhere, while JPG to PNG serves a narrower but specific need — feeding a photographic image into a workflow (editing, compositing, print production, icon creation) that assumes or requires a lossless, alpha-capable format at the input stage.
Once you have the PNG, Image Compressor can shrink it back down without losing transparency, or convert to WebP for an even smaller web-ready file.
