Why convert JPG to PNG?
Before anything else, the most important thing to understand about this conversion — because it's the source of most disappointment with it:
Converting JPG to PNG does not improve image quality. JPG is a lossy format. When an image was first saved as JPG, real detail was permanently discarded, and no conversion can reconstruct it. Compression artefacts baked into the JPG will be faithfully, losslessly preserved in your new PNG.
That's not a reason to avoid the conversion. It's a reason to be clear about what it's for: this conversion is about stopping future loss and gaining capabilities JPG doesn't have, not repairing past loss.
Generation loss — the real problem it solves
Every time you open a JPG, edit it, and save it as JPG again, the lossy compression runs again on an already-compressed image. Do this five or six times and the degradation becomes obvious: colours band, fine detail smears, and blocky squares appear around edges. This is called generation loss, and it's cumulative and irreversible.
Converting to PNG at the start of an editing workflow stops that cycle. PNG is lossless, so you can open, edit, and save as many times as you like with no further degradation. Convert once at the beginning, work in PNG, then export to whatever delivery format you need at the end. This one habit prevents a category of quality problem that's very difficult to diagnose after the fact.
Transparency
JPG has no alpha channel — it physically cannot store transparency. PNG can. If you need to remove a background, place a logo over a coloured surface, or composite an element onto other artwork, you need to be working in a format that supports transparency.
Note the direction of causality here: converting to PNG doesn't create transparency, it makes transparency possible. Your converted PNG will still have whatever solid background the JPG had. What's changed is that you can now erase that background in an editor and have the result actually save as transparent.
Text, screenshots, and sharp edges
JPG was engineered for photographs — smooth gradients, organic detail — and it handles them well. It handles hard edges badly. Text, UI elements, line drawings, and flat colour blocks develop visible "ringing": faint halos and mosquito-like noise around every sharp boundary.
This is why a screenshot saved as JPG looks subtly grubby, especially at small text sizes, while the same screenshot as PNG looks clean. If you're working with interface captures, diagrams, charts, or anything containing text, PNG is the correct format and JPG never was. Converting won't remove the ringing already present, but it will stop it getting worse — and for future captures, save as PNG in the first place.
What to expect from the file size
Your PNG will be larger than the JPG, frequently several times larger. This is normal and expected. PNG's lossless compression simply cannot match JPG's aggressive photographic compression, and the "cost" is the price of not discarding data.
One counter-intuitive effect worth knowing: converting a heavily compressed JPG to PNG can produce a surprisingly large file, because PNG now has to losslessly encode all the compression artefacts as though they were genuine image detail. Noise is expensive to store losslessly. If size matters and you don't need lossless editing, WEBP is usually a better destination — see the PNG to WEBP converter for that trade-off.
How this converter works
Your browser decodes the JPG with its native image engine, draws it onto an off-screen canvas, and re-encodes it as PNG. Everything runs inside this browser tab — the image is never uploaded to a server, so client photographs and unreleased work stay on your machine.
When to just keep the JPG
If the image is a photograph, you're not going to edit it further, and you just need to view, send, or publish it, converting to PNG gains you nothing and costs you file size. JPG remains an excellent format for finished photographic content. Convert when you're about to work on the image, or when you need transparency or crisp edges.