Understand when to use PNG vs JPG, how to convert between them, and how to keep images looking sharp while reducing file size.
PNG and JPG look the same to the eye, but under the hood they work very differently — and using the wrong one can either bloat your website or blur your photos. If you have ever uploaded an image and been told it is "too large," or converted a file and been disappointed by the result, this guide explains what is actually happening and how to get it right.
PNG is lossless. It stores every pixel exactly, which makes it great for screenshots, logos, diagrams, and anything with text or sharp edges. JPG is lossy. It throws away visual information in ways humans tend not to notice, which makes the file much smaller — perfect for photographs.
A photograph saved as PNG can easily be 10 times larger than the same photo saved as JPG, with no visible difference. A screenshot of text saved as JPG, on the other hand, often looks fuzzy around the letters.
There are three common routes:
When saving a JPG, you choose a quality level from 0 to 100. Anything above 85 is usually indistinguishable from the original by eye, while being dramatically smaller than a PNG. Below 70, compression artifacts (blockiness, color bleeding around edges) start to show.
A good default for web use: 80–85 quality. For archive-worthy photos, 90 is safe.
PNG supports transparent backgrounds. JPG does not. When you convert a PNG with transparency to JPG, the transparent areas get filled in — usually with white, sometimes with black. If your logo was transparent, it will now have a white square around it.
If you need transparency, stick with PNG or WebP. Never convert a transparent graphic to JPG.
If your image is too large, resizing its pixel dimensions has far more impact than changing the format. A 4000×3000 photo at 85% JPG is about 2 MB. Resize it to 1600×1200 at the same quality and it drops to around 400 KB — without any visible difference on a normal screen.
Match the format to the content: PNG for graphics, JPG for photos, WebP when you want the best of both. Always resize before compressing, keep quality around 85, and check transparency before converting. Those three habits cover 95% of the image problems people run into.