A 442 KB photo of a coffee cup, saved as PNG, became a 54 KB JPG: 88% smaller, same 600×400 pixels. A 256×256 logo on a transparent background went the other way, from 1.1 KB to 5.7 KB, and lost its transparency. Those two results sum up when this conversion helps.
Worth converting, or not
| The PNG is | Convert to JPG? | Why |
|---|---|---|
| A photo (camera, phone, exported from an editor) | Yes | Much smaller: the coffee photo lost 88% |
| A scanned photo or document page | Usually | Same reason, but check small text afterwards |
| A screenshot with text | No | Text gets smudgy and the file may grow |
| A logo, icon or diagram | No | Flat colors are already tiny in PNG |
| Anything with a transparent background | No | The background turns white |
Why the logo grew
PNG compresses by spotting repetition: a logo that is mostly one color with clean edges takes very few bytes. JPEG works on 8×8 blocks of pixels and describes each block as a mix of smooth patterns. That suits photos, where colors blend, but a hard edge between two flat colors needs many patterns to draw, and what JPEG cannot afford it smears into faint noise. So a 1.1 KB logo costs 5.7 KB as a JPG and looks worse. A photo has no such edges to protect, which is how the coffee cup lost 88%.
The transparent background turns white
JPG cannot store transparency. The converter puts the image on white before saving, rather than letting those areas turn black. On a white web page that looks fine; on a colored background the white box shows.
Files that are not PNG
Drop a JPG here and the tool says it is already JPG. Drop a HEIC, WebP or AVIF and it becomes a JPG too: the converter reads all of them on every page.
If the JPG is still over a size limit, Compress image can lower the quality, or Resize image can reduce the pixel dimensions.