What the common image formats are, how they differ, and which one fits the job in front of you.
An image format is a way of storing a picture as a file. Different formats make different trade-offs between file size, quality, transparency and compatibility, which is why the same photo can be 3 MB as one type and 300 KB as another. Picking the right one can make a web page load faster, get a photo accepted by an upload form, or keep a logo crisp.
JPG, also written JPEG, is the format almost every camera, phone, website and form understands. It uses lossy compression, which means it throws away detail the eye is least likely to notice in order to make the file smaller. You choose how much to throw away, and the more you discard, the smaller and blurrier the file gets.
JPG is excellent for photographs and poor for sharp lines, text and flat colours, where its artefacts show as fuzz around the edges. It cannot store transparency. If a form asks for a photo, JPG is almost always the format it means.
PNG uses lossless compression, so nothing is thrown away and the picture comes out exactly as it went in. That makes it the right choice for logos, screenshots, diagrams and anything with text or hard edges, and it supports transparent backgrounds.
The cost is size. A photograph saved as PNG is usually several times larger than the same photograph as a JPG, so PNG is a poor choice for ordinary photos.
WebP was created by Google to replace both JPG and PNG on websites. It can do lossy and lossless compression and supports transparency. Google's own tests found its lossy files to be roughly a quarter to a third smaller than JPG at comparable quality, which is why many websites use it.
WebP is now supported by all the major browsers. Where it still causes trouble is outside the browser: some older apps, editors and upload forms do not accept it, which is why people often need to convert a downloaded WebP image to JPG or PNG.
AVIF is a newer format that often produces even smaller files than WebP at the same visual quality. Browser support has grown quickly, but support in editing software and upload forms is still patchy, so it suits websites more than files you plan to share.
HEIC is the format iPhones use by default. It stores photos in much less space than JPG, but many Windows and Android programs and most upload forms do not accept it. If you have iPhone photos that will not open or upload, converting them to JPG fixes the problem.
For an upload form, use JPG for photos and signatures unless the form names another format. For a logo, a screenshot or an image with text, use PNG. For your own website, WebP is a good default, with JPG as a fallback. For photos you will send to other people or open on different devices, JPG is the format least likely to cause a problem. For iPhone photos headed anywhere outside Apple's own apps, convert HEIC to JPG first.
Converting is simple, but remember that going from a lossy format to another lossy format loses a little more quality each time, and converting a JPG to PNG does not bring back detail that is already gone. Keep your original, convert a copy, and check the result. Tooqly converts between JPG, PNG, WebP and HEIC in your browser, so the image is not uploaded.
Convert an image between formats
It usually makes smaller files at similar quality and supports transparency, so it is better for websites. JPG is still the most widely accepted format, so it is better for sharing and for upload forms.
Yes, a little, because JPG is lossy. For a photograph it is rarely noticeable. For a screenshot or logo with sharp edges and text, keep the PNG.
Many forms only accept JPG, PNG or PDF. Converting the image to JPG, usually in a few seconds, solves it.