The quick answer
Use JPG for photographs, PNG when you need transparency or pixel-perfect graphics, and WebP when you want the best of both at a smaller size. That one sentence covers most decisions — but the details are worth understanding so you can choose confidently in edge cases.
JPG: built for photographs
JPG uses lossy compression tuned for the kind of smooth tonal variation you find in photos. It produces small files for complex images and is supported absolutely everywhere. The downside is that it discards data permanently, it can't store transparency, and it struggles with sharp edges and text, where it introduces visible halos.
Reach for JPG when the image is a photo and you don't need a transparent background.
PNG: for graphics and transparency
PNG is lossless, so it preserves every pixel exactly. It supports full alpha transparency, which makes it the go-to for logos, icons, screenshots and any graphic that sits on top of other content. The trade-off is file size: a photo saved as PNG can be several times larger than the same image as JPG.
Choose PNG when you need transparency or crisp, exact detail in flat graphics.
WebP: the modern all-rounder
WebP supports both lossy and lossless modes and transparency, and it typically produces files 25–35% smaller than JPG or PNG at comparable quality. Browser support is now effectively universal, which makes it an excellent default for the web.
The main reason to avoid WebP is compatibility with old desktop software that predates it — in which case convert to JPG or PNG for that specific use.
A note on transparency
Only PNG and WebP can store transparency. If you convert a transparent PNG to JPG, the transparent areas have to be filled with a solid color — usually white. Good conversion tools let you choose that background color so you're not surprised by the result.
Converting without uploads
Format conversion is pure pixel work, which means a browser can do it entirely on your device. Drop in a file, pick the target format and quality, and export — no server sees your image. That's especially valuable for brand assets and client work you'd rather not send to an unknown service.
Choosing in practice
Photo for the web? WebP, falling back to JPG. Logo or screenshot with transparency? PNG or lossless WebP. Need maximum compatibility with old tools? JPG or PNG. When in doubt, convert a copy and compare the file size and quality side by side.
