The short answer
Use JPG for photographs when small files and broad compatibility matter. Use PNG for graphics that need lossless pixels or alpha transparency. Use WebP for modern web delivery when you want efficient photographic or transparent images and your target software supports it.
No format wins every comparison. A logo, a camera photo, and a screenshot contain different visual information, so they respond differently to compression.
How the formats differ
| Format | Compression | Transparency | Good fit |
|---|---|---|---|
| JPG/JPEG | Lossy | No alpha channel | Photographs and complex colour gradients |
| PNG | Lossless | Yes | Logos, interface graphics, diagrams, screenshots |
| WebP | Lossy or lossless | Yes | Web images where modern format support is acceptable |
Lossy compression discards information to reduce size. At sensible settings this can be difficult to notice in a photograph, but repeated lossy exports can introduce ringing, blocking, or blurred detail. Lossless compression reconstructs the encoded pixels exactly, although it cannot restore information discarded before the file was created.
Practical choices
- Camera photograph: start with JPG or lossy WebP. PNG usually stores photographic noise inefficiently.
- Logo over changing backgrounds: use transparent PNG or WebP.
- Screenshot with small text: PNG often keeps sharp edges; WebP lossless can also work.
- Email attachment: choose the format the recipient can open, then resize before compressing.
- Long-term editable master: keep the highest-quality original separately from web derivatives.
What conversion can and cannot do
Changing a JPG to PNG does not improve the source. The PNG can preserve the already-decoded pixels without another lossy export, but JPEG artifacts and missing detail remain. Changing PNG to JPG removes transparency and introduces lossy encoding; transparent pixels need a chosen background colour.
File extensions are not quality settings. Dimensions, encoder settings, image complexity, colour handling, and metadata all affect the result. Compare the actual output visually instead of assuming a format name guarantees a smaller or sharper file.
A sensible workflow
- Keep an untouched original.
- Crop and edit before making delivery copies.
- Use the Resize Image tool to create the required pixel dimensions.
- Use Compress Image to balance bytes and visible quality.
- Inspect transparency, fine text, gradients, and metadata before publishing.
Tools and related reading
Next, read how image compression works or how to resize without distortion. Format conversion and compression solve different problems, so decide which constraint you are addressing first.