JPG vs PNG: which should you use?

JPG and PNG are both ways of packing pixels into a smaller file, but they go about it in opposite ways — and that one difference decides almost everything else about when to use each. Get the compression right for the image in front of you, and the rest (file size, sharpness, whether it supports transparency) mostly follows on its own.

What is the difference between JPG and PNG?

JPG (JPEG) uses lossy compression. To shrink the file, it permanently throws away some of the image data — detail a viewer is unlikely to notice, mostly small colour variations. That’s a great trade for a photograph, where colours shift gradually across the frame anyway. It’s a bad trade for anything with hard edges: text, line art and flat-colour graphics come out of JPG compression with a soft, smudgy fringe around every sharp transition, usually called compression artefacts.

PNG uses lossless compression. It packs the file more efficiently, but every pixel comes back out exactly as it went in — nothing is discarded. That makes PNG the right choice whenever exactness matters: a screenshot, a logo, a chart, a scanned document, anything with legible text in it. The cost is file size: a PNG of a genuine photograph is often several times larger than a JPG of the same photo, for a difference most people would never spot.

Is PNG better quality than JPG?

Technically, yes: a PNG is an exact copy of the pixels, while a JPG is always a close approximation. In practice, a JPG saved at a high quality setting is visually indistinguishable from the original for most photos, and far smaller. Where the gap shows is on sharp detail — zoom into a JPG of a screenshot and you’ll see faint blotches around the text that a PNG simply doesn’t have. So “better quality” really depends on what’s in the picture.

Transparency: the other big difference

PNG has a built-in alpha channel, so any pixel can be fully opaque, fully see-through, or anywhere in between — which is how a logo sits cleanly on a coloured background instead of arriving with a white box around it. JPG has no equivalent. Save a transparent PNG as a JPG and every transparent area is filled with a solid colour, almost always white. If a transparent background matters, PNG isn’t just the better option — it’s the only one of the two that works.

Why repeated saving hurts JPG but not PNG

JPG’s lossy compression is applied again every time the file is saved, so each edit-and-save cycle discards a little more detail (often called generation loss). Re-saving a PNG changes nothing. The practical rule: keep a working copy as PNG while you’re still editing, and export to JPG once, at the end.

Are JPG and JPEG the same thing?

Yes. They’re the same format with two spellings of the file extension. .jpg dates from older versions of Windows, which only allowed three-letter extensions; .jpeg is the full name. Any app that opens one opens the other, and renaming between them changes nothing about the image.

How to convert PNG to JPG

The most common reason to go this way is size: a form or upload box only accepts JPG, or a photo saved as PNG is too big to email. With Altto’s PNG to JPG converter:

1. Add your PNG images — drop in one file or a whole batch.
2. Choose a quality setting. Standard gives smaller files for everyday sharing; High stays closer to the original at a larger size. Both use a high JPG quality setting.
3. Save your JPGs. A single image downloads directly; several come back together in a .zip.

The conversion happens with your browser’s own built-in image tools, inside the tab, so the files never leave your device. One thing to know before converting: any transparent areas in the PNG are filled with white, because JPG can’t store transparency. For a logo that needs to sit on a coloured background, keep the PNG.

Without a converter: on Windows, open the PNG in Paint and use File → Save as → JPEG picture. On a Mac, open it in Preview, choose File → Export, and pick JPEG from the Format menu (you’ll get a quality slider too). Both are fine for one or two images; a batch tool is quicker for a folder full.

How to convert JPG to PNG

Going the other way is useful when a tool or template specifically asks for a PNG, or when you want to keep editing an image without adding any further JPG loss. Altto’s JPG to PNG converter works the same way: add the files, convert, save. Two honest caveats:

• It won’t improve quality. Converting stops any further loss, but it can’t restore detail the JPG already threw away.
• It won’t make the background transparent. The PNG keeps whatever background the photo had. To cut the subject out, use the Background Remover instead, which gives you a transparent PNG — our guide on removing the background from a photo walks through it.

Expect the PNG to be noticeably larger than the JPG it came from. That’s normal: lossless compression simply can’t pack photographic detail as tightly.

What about WebP and HEIC?

WebP supports both lossy and lossless compression in one format, plus transparency, and is usually smaller than either JPG or PNG at similar quality. The catch is compatibility: some older software and upload forms still expect a plain JPG or PNG, which is usually the reason to convert one. HEIC is the default photo format on iPhone; it compresses more efficiently than JPG, but support outside Apple’s own apps is patchy, so HEIC photos often need converting before they’ll open or upload elsewhere — see how to convert HEIC to JPG.

Other free image tools

For the formats above there’s also WebP to JPG, WebP to PNG and HEIC to JPG, and if you only need a smaller file without changing format, Compress Image shrinks a JPG or PNG. Like the converters, they all run inside your browser tab, so the image is never uploaded.

Common questions

Sources

Where the PNG facts in this guide come from:

• W3C — PNG (Portable Network Graphics) Specification, Version 1.0 (lossless compression and the optional alpha channel for transparency)