Image format choice affects file size, transparency, sharpness and how well an image survives later editing. The useful question is not “which format is best?” but “what kind of image is this, where will it be displayed, and do I need transparency or lossless detail?” A photograph, a logo and a screenshot often deserve different formats.
Start with the visual content
Photographs contain many gradual color changes and usually compress well with lossy formats. Logos, diagrams, UI screenshots and text-heavy graphics contain hard edges that can reveal compression artifacts quickly. Before converting, identify whether the image behaves more like a photo or more like a graphic.
Use JPEG when photographic compatibility matters
JPEG is a practical choice for photographs and other continuous-tone images when transparency is not required. It is lossy, so quality is traded for a smaller file. Keep a higher-quality master and export a delivery copy rather than repeatedly reopening and resaving the same JPEG.
Use PNG for lossless graphics and transparency
PNG uses lossless compression and supports transparency. It is useful for screenshots, diagrams, icons and graphics where crisp edges matter. It can become unnecessarily large for full-resolution photographs, so do not choose PNG only because it sounds “higher quality.”
Use WebP for efficient web delivery
WebP supports lossy and lossless compression as well as transparency. It is widely supported by modern browsers and can be an efficient delivery format for many websites. Still keep the source file in an editing-friendly format if you expect to revise the artwork later.
Compare at the real display size
A format decision should be tested at the size users will actually see. Export two or three versions, compare fine text, edges, gradients and transparency, then choose the smallest file that still looks appropriate. A 4K comparison at 400% zoom can exaggerate differences that are irrelevant on a 900-pixel content column.
Do not confuse format conversion with resizing
Changing PNG to WebP does not automatically fix oversized dimensions. If an image is much larger than its display area, resize first, then choose the format and compression level. This avoids storing and transmitting pixels the page does not need.
Worked example
Example workflow
A product photo for a web page can be cropped first, resized to the largest display width, exported as WebP and compared with a JPEG version. A transparent logo from the same page may be better kept as PNG or SVG because it needs clean edges and transparency.
Practical checklist
Before you finish
- Keep an original master before converting.
- Use PNG when transparency and crisp lossless edges are important.
- Use JPEG for many photographs when broad compatibility and simple lossy compression are useful.
- Test WebP as a web-delivery option and compare the actual visual result.
- Resize oversized images before final compression.
Common mistakes
What to avoid
- Saving every photograph as PNG and creating huge files.
- Repeatedly resaving a JPEG until visible artifacts build up.
- Converting formats without checking transparency.
- Judging quality only while zoomed far beyond the intended display size.
Further reading from authoritative sources
Use these references when you need the underlying specification or platform guidance.