Choosing an Image Format: JPG, PNG, WebP and PDF

Four formats cover almost every everyday need: JPG, PNG, WebP and PDF. Each makes a different trade-off between size, quality and capability. The right choice depends on the content of the image and where it will be used, not on which format happens to be the default on your device.

JPG: photographs and smooth detail

JPG uses lossy compression, discarding subtle detail to shrink the file. It handles photographs, gradients and skin tones well because the eye tolerates small losses in those areas. It cannot store transparency, and repeated re-saving gradually degrades quality. Use JPG for photos that will be shared or published, and avoid editing and re-saving the same JPG many times.

PNG: sharp edges and transparency

PNG is lossless, so it preserves every pixel exactly. That makes it ideal for screenshots, logos, icons, charts and diagrams, where crisp edges matter and artefacts are obvious. It supports transparency, which is essential for a logo placed on a coloured background. The cost is size: a photographic PNG can be several times larger than the equivalent JPG.

A common mistake is exporting a photograph as PNG "for quality". The file becomes large without looking better, because the source had no sharp edges to preserve.

WebP: smaller files for the web

WebP supports both lossy and lossless modes, plus transparency, and generally produces smaller files than JPG or PNG at comparable quality. Modern browsers display it without trouble. The caveat is compatibility with older software: some desktop publishing tools and image editors still refuse to open WebP, so keep a JPG or PNG master if the image may be reused elsewhere.

PDF: a document, not a picture

PDF is the right format when the file must print predictably, keep multiple pages together, or preserve selectable text. It can embed images, fonts and vector graphics in one container. It is a poor choice for a single photo you want to drop into a chat, and a poor choice for editing, because PDF editing is page-oriented rather than pixel-oriented.

A quick decision list

1. Is it a photograph? Use JPG, or WebP if it is for a website and you control the markup.
2. Does it need transparency? Use PNG, or WebP where browser support is acceptable.
3. Is it a screenshot, chart or logo? Use PNG to keep text and edges sharp.
4. Does it contain text that must stay selectable? Use PDF.
5. Must it print identically on another machine? Use PDF.
6. Is the upload limit the main constraint? Resize first, then choose JPG or WebP.

Colour and transparency pitfalls

Converting a transparent PNG to JPG fills the transparent area with white, which can look wrong on a dark background. Converting a CMYK print image to RGB for the web can shift colours. If an image looks different after conversion, check the colour mode and the background handling before assuming the tool failed.

Also consider animation. Animated GIFs and animated WebP files lose their animation when converted to a still format. Only the first frame is kept, so extract frames deliberately if that is what you need.

Keeping a master copy

Store the highest-quality version you have and export smaller versions from it. Converting a compressed JPG to PNG does not restore lost detail; it only wraps the existing pixels in a larger container. The master is what you return to when a new use case appears.