JPG vs PNG vs WebP: which format should you use?
The right file format depends on what your image contains and where you plan to upload it. A smaller file is not always a better file if the receiving website rejects that format.
| Format | Often best for | Transparency | What to consider |
|---|---|---|---|
| JPG | Photographs and widely compatible application photos | No | Lossy; details can soften at low quality |
| PNG | Screenshots, logos, illustrations and crisp text | Yes | Lossless PNG may be larger for photographic content |
| WebP | Modern websites and compact photos/graphics | Yes | Check destination portal support before using |
When to choose JPG
JPG is usually a good option for photos and many online application systems. It uses adjustable lossy compression: smaller files may have visible artifacts, especially around fine text or high-contrast boundaries. JPG does not support transparent areas; the compressor fills those areas with white.
When to choose PNG
PNG is useful where sharp edges, labels or transparency matter. This compressor exports PNG using the browser's lossless encoder. A quality slider cannot force lossless PNG into an arbitrarily tiny file, so reducing dimensions may be necessary.
When to choose WebP
WebP often combines efficient compression with transparency support. It is commonly supported in modern browsers. However, government forms, visa sites and older content-management tools may still insist on JPG or PNG. Check allowed file extensions first.
What does the Auto output setting do?
On CompressKBNow, Auto preserves JPEG output for JPEG inputs and uses WebP for PNG/WebP inputs. It is designed to balance compatibility and file-size reduction, but it does not know the receiving website's rules.
How to choose under strict KB limits
- Check what formats the form accepts.
- Choose your format on the compressor.
- Set the required maximum KB and compress.
- Inspect the resulting image for legibility and file size.
Remember: A smaller output may have reduced dimensions, regardless of which format you select. Keep your original file as a backup.