JPG vs PNG vs WebP: Which Image Format Should You Use?

The short answer

JPEG: the universal photo format

JPEG (files ending in .jpg or .jpeg) has been the standard photo format since the 1990s. It uses lossy compression: it splits the image into small blocks and discards fine detail and colour information that the eye is least sensitive to. That makes it very efficient for photographs, which are full of gradual changes in colour and texture.

Its weaknesses show on hard edges. Text, line art and flat graphics often develop faint smudges or "ringing" around edges. JPEG also cannot store transparency, so transparent areas must be filled with a solid colour.

Use JPEG when compatibility matters most: virtually every device, app, printer and upload form accepts it.

PNG: lossless and transparent

PNG stores images losslessly: every pixel comes back exactly as it was saved. It supports full transparency (an alpha channel), which makes it the traditional choice for logos, icons and interface graphics.

Because it is lossless, PNG is a poor fit for photos. A photo saved as PNG is typically several times larger than the same photo as a good-quality JPEG. Screenshots, diagrams and graphics with large flat areas, on the other hand, compress well as PNG and stay perfectly crisp.

PNG files can still be made smaller in two ways: lossless re-optimisation, or reducing the number of colours to a palette of 256 or fewer. Both are covered in our guide to reducing PNG size while keeping transparency.

WebP: the modern all-rounder

WebP was developed by Google and supports both lossy and lossless compression, transparency in both modes, and animation. Google’s published comparisons found lossy WebP files roughly 25–34% smaller than JPEG files of comparable quality; actual savings depend on the image and the encoder settings.

Every current major browser displays WebP, including Safari since version 14, and most modern operating systems and image editors can open it. Some older software, email clients and printing services may still not accept it, so check before using it outside the web.

SlimMyFile encodes WebP with the official libwebp encoder compiled to WebAssembly, so the result does not depend on whether your browser can create WebP files itself. Try it with the WebP compressor.

What about newer formats?

AVIF and JPEG XL can compress even better than WebP in many cases, but support across browsers, apps and services is still uneven. For files you share widely today, JPEG, PNG and WebP remain the safe choices. SlimMyFile currently works with these three formats only.

How to convert between formats

1. Open the image compressor and add your images.
2. Under Output format, choose JPEG, PNG or WebP, or keep the original format.
3. Adjust the quality for JPEG and WebP, or the PNG mode for PNG.
4. If you convert a transparent image to JPEG, pick a background colour for the transparent areas.
5. Compress, compare before and after, and download the files individually or as a ZIP.

Common mistakes

• Saving photos as PNG "for quality". The file becomes much larger, and the quality advantage is invisible at normal viewing sizes.
• Saving screenshots as low-quality JPEG. Text becomes fuzzy; use PNG or high-quality WebP instead.
• Converting a JPEG to PNG to "restore" quality. Detail lost by JPEG compression cannot be recovered; the PNG will only be bigger.
• Converting a transparent logo to JPEG without choosing a background colour that matches where it will be used.

Frequently asked questions