It feels backwards. JPG is the small format and PNG is the heavy one. So you convert a PNG to JPG to save space, and the new file comes out bigger. It looks like a bug.
It isn't. It's how the two formats work, and it happens most with screenshots, logos, and anything made of flat color and text.
Two Different Ways to Shrink an Image
PNG uses lossless compression. It works a bit like a zip file. It finds repeated patterns and stores them once. A flat background, a solid icon, or a line of crisp text repeats a lot, so PNG squeezes it down well.
JPG works another way. It cuts the picture into small blocks and smooths the color changes inside each block, dropping detail your eye is unlikely to miss. That's great for photos, where colors blend gradually from one pixel to the next.
A sharp edge has no gradual blend. Think of the edge of a letter. JPG has to store extra detail at every edge instead of one simple repeated pattern. On a picture that's mostly edges and flat color, that adds up fast.
Where This Happens Most
Screenshots are the classic case. A typical one is flat panels and small text, which is close to the worst case for JPG. Logos, simple diagrams, pie charts, and memes on a solid background have the same problem. PNG was already the better fit, so converting works against the picture.
When JPG Wins
JPG isn't a worse format. It's built for a different picture. On a real photo, with smooth skies, skin tones, and textures, JPG has plenty to work with and usually beats PNG by a wide margin. The trouble only starts when photo compression meets a graphic.
Quick Comparison
| Content Type | Better Format |
|---|---|
| Screenshot or UI panel | PNG |
| Logo or icon | PNG |
| Chart or diagram | PNG |
| Photograph | JPG |
| Scanned photo with gradients | JPG |
How to Fix an Oversized File
If the picture is a screenshot or a logo, the easiest fix is to keep it as PNG. If you really need a JPG, say because a form only accepts that extension, lower the quality setting. Flat graphics have little fine detail to damage, so a lower setting often works better than it would on a photo. Our Image Compressor shows the new file size before you download.
Not sure which format will be smaller for your picture? Our Image Converter lets you try both and compare, so you don't have to guess.
A Quick Check Before You Convert
Look at what's in the picture. Mostly solid color, text, or sharp shapes, like a screenshot, a slide, or a logo? PNG is probably the better fit. A photo with soft light and gradual color changes? JPG will almost always come out smaller. That two-second look settles most cases.
Size isn't the only thing at stake. Even when a JPG is a bit smaller, it adds compression artifacts around every edge and letter. For documentation screenshots or a brand logo, sharpness matters more than a few saved kilobytes, so keep the PNG.
Frequently Asked Questions
Why is my PNG smaller than my JPG?
It happens with screenshots, logos, and diagrams. PNG is very good at squeezing flat color and repeated patterns. JPG is built for the smooth gradients in photos, and it does worse on sharp edges and text.
Should I always use PNG for screenshots?
Almost always. Screenshots are flat color and sharp edges, which is what PNG handles best. Saving one as JPG usually makes the file bigger and leaves fuzzy marks around the text.
Does converting PNG to JPG always make the file smaller?
No. It reliably shrinks photos. For flat graphics like screenshots, logos, and icons, the JPG can be the same size or bigger.
What is the best file format for screenshots?
PNG. It keeps text and interface edges sharp with no compression artifacts, and it's usually the smaller file for that kind of picture too.
What are compression artifacts?
They're the fuzzy specks and blocky patches JPG can leave around sharp edges and small text. They're a side effect of throwing away detail to save space.
Sources and further reading
- Portable Network Graphics (PNG) Specification (W3C) How PNG compresses images without losing data.
- Image file type and format guide (MDN Web Docs) When lossy and lossless formats each make sense.