PNG vs JPG: When to Use Which (and What Transparency Costs You)
A practical comparison — which format wins for photos, screenshots, logos and charts, and the transparency trap that ruins logos during conversion.
Both formats have been around for decades and both are supported everywhere. The choice is not about quality in the abstract — it is about what kind of image you have.
The one-line summary
JPG for photographs. PNG for anything with text, flat colour, sharp edges, or transparency.
Why photographs go to JPG
A photograph has smooth gradients and continuous tone everywhere. JPEG throws away high-frequency detail that the eye barely notices in that kind of content, and in exchange the file gets dramatically smaller — often 5 to 10 times smaller than PNG for the same photo.
Why everything else goes to PNG
PNG is lossless, so it reproduces hard edges exactly. Screenshots, logos, charts, maps, and UI captures are full of hard edges and flat colour, which is precisely what JPEG handles worst: it turns crisp edges into fuzzy halos and ringing artifacts, and it does so at any quality setting. On top of that, PNG supports transparency and JPEG does not.
The transparency trap
This is where conversions usually go wrong. A PNG logo on a transparent background, converted to JPG, has to put something behind those pixels. Some tools produce a black background, which quietly destroys the logo for anyone using it on a light page.
This converter composites transparent areas onto white before encoding, and tells you in advance when your file has an alpha channel. If you need a different background colour, flatten the image in an editor first.
A second trap: the file can get bigger
Counter-intuitively, a screenshot or flat-colour logo converted to JPG is often larger than the PNG it came from, because JPEG spends bits representing sharp edges as smeared detail. This tool checks for that: if the JPG would be bigger than your input, it keeps your original file and says so, rather than handing you a worse file that is also larger.
Colour detail on synthetic images
JPEG normally reduces colour resolution because human eyes are less sensitive to it. On synthetic images — logos, charts, coloured text — that reduction is visible, because the colour transitions are perfectly sharp. This converter keeps full colour resolution by default, which costs some bytes and is the right trade for this kind of content.
Quick reference
- Photo from a camera or phone → JPG at quality 80–90.
- Screenshot → PNG, unless you need JPG for a specific upload form.
- Logo or icon with transparency → PNG, or JPG only if you can accept a solid background.
- Chart or map → PNG.
- Something that must be under a size limit → start from the largest acceptable dimensions, then convert.
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