The right format depends on what is in the picture and where it will be used. The short version: JPG for photos, PNG for graphics and screenshots, and WebP or AVIF when you want smaller files for the web.
JPG (JPEG)
Best for photographs. It uses lossy compression: it throws away detail your eye is unlikely to miss, which gives small files. It does not support transparency, and repeatedly re-saving a JPG slowly degrades it. Quality settings around 75 to 85 are a good balance for most photos.
PNG
Best for logos, icons, diagrams and screenshots. It is lossless, so edges and text stay crisp, and it supports transparency. The cost is size: a photo saved as PNG can be many times larger than the same photo as a JPG.
WebP
A modern format that handles both photos and graphics, with transparency, usually at a smaller size than JPG or PNG. Current browsers all support it. Some older apps and e-mail clients and some upload forms still do not accept it, which is the main reason people convert WebP back to JPG or PNG.
AVIF
Often the smallest at similar quality, but slower to create and not accepted everywhere yet. Good for websites that can serve a fallback.
A simple rule
- Photo for a website: WebP (or JPG if you need maximum compatibility).
- Logo, icon or screenshot: PNG, or WebP if size matters.
- Needs a transparent background: PNG or WebP, never JPG.
- A form or app rejects your file: convert to JPG or PNG.
- Printing: JPG at high quality or PNG, not a heavily compressed web image.
When you convert to a format without transparency, transparent areas have to become a solid colour. ToolGalaxy fills them with white and tells you when it does.