JPG and PNG are the two image formats almost everyone runs into, and on screen they often look identical. But under the hood they work in completely different ways — and picking the wrong one means either a blurry image or a file that's needlessly huge. Here's how to choose in five seconds, plus when you should skip both and use a PDF.
The one-sentence answer
Use JPG for photographs. Use PNG for screenshots, logos, text, and anything with sharp edges or transparency. That single rule covers about 90% of real-world decisions. The rest of this article explains why, so you can handle the other 10% with confidence.
How JPG works (and where it shines)
JPG (also written JPEG) uses lossy compression. It throws away detail your eye is unlikely to notice in exchange for dramatically smaller files. For photographs — with their smooth gradients and millions of subtly different colors — this is a brilliant trade: a photo that would be 20 MB as a lossless file might be a crisp 2 MB as a JPG with no visible difference.
The catch is that JPG re-compresses every time you save. Edit and re-save a JPG repeatedly and you'll slowly accumulate ugly blocky artifacts. JPG also can't store transparency, so a logo saved as JPG gets a solid (usually white) background.
- Great for: photos, realistic images, anything you'll mostly view rather than edit.
- Bad for: screenshots of text, logos, line art, images needing a transparent background.
How PNG works (and where it shines)
PNG uses lossless compression — it shrinks the file without throwing away a single pixel. That makes it perfect for images where every edge needs to stay razor-sharp: UI screenshots, diagrams, charts, logos, and text. PNG also supports transparency, which is why almost every logo on the web is a PNG.
The downside is size. For a photograph, a PNG can be five to ten times larger than the equivalent JPG, for no visible benefit. Use PNG on a photo-heavy web page and you'll slow it to a crawl.
- Great for: screenshots, logos, icons, diagrams, anything with text or transparency.
- Bad for: large photographs where file size matters.
So when should you convert to PDF instead?
JPG and PNG are great for viewing an image. But the moment you need to submit, print, or archive it, a PDF is usually the better container. Here's why:
- It's the format people actually ask for. University portals, job applications, expense systems, and government sites almost always want a PDF — a raw phone photo can get rejected.
- It prints predictably. A PDF prints the same on every printer; a loose image can scale or rotate in surprising ways.
- It bundles multiple pages. Three screenshots become one tidy three-page PDF instead of three separate files.
- It's harder to alter by accident, which matters for receipts, contracts, and proof of payment.
You don't have to choose a format and stick with it forever. Keep the screenshot as a PNG for editing, then export a PDF when it's time to send it somewhere official.
Converting, the private way
PDFduck converts JPG and PNG images to PDF entirely inside your browser — the image never gets uploaded anywhere. Transparency on a PNG is flattened cleanly onto a white page, and JPG quality is preserved at full resolution. It's free, unlimited, and works on your phone.
Convert an image to PDF →The cheat sheet
- Photo you'll post or email → JPG.
- Screenshot, logo, or diagram → PNG.
- Anything you'll submit, print, or archive → convert it to PDF.