Image encoding decisions
JPG, PNG or WebP: which format should you use?
Start with the formats the upload form accepts. JPG often suits photos; PNG keeps sharp edges and transparency. WebP is another option when the destination supports it. Check the saved result before sharing.
On this page
Choose for the picture and its destination
A small file is useful only if the destination accepts it. Read the format rule before changing size or quality.
For photos, compare JPG and WebP at the size you need. For logos, screenshots, and small text, check PNG first. Zoom in to check edges and lettering.
| Your file | Start with | Check |
|---|---|---|
| Photo for an upload form | JPG if the form accepts it | Faces, fine detail, and the size limit |
| Logo with a clear background | PNG, or WebP if accepted | Transparency on the final background |
| Screenshot with small text | PNG, then compare a smaller alternative | Readability at the intended display size |
| Photo for a website | WebP or JPG | Browser support, appearance, and bytes |
Try it with a safe sample
What happens to a transparent background?
This PNG has a transparent corner. Converting it to JPG with a white background makes that corner opaque.
- Download the transparent sample.
- Choose JPG and a white background, then export.
- Check the corners before using the copy on a colored page.
| PNG source | 11,236 B |
|---|---|
| JPG output | 6,941 B |
| Source corner RGBA | 0, 0, 0, 0 |
| Output corner RGBA | 255, 255, 255, 255 |
JPG cannot retain transparency. Use PNG or supported WebP when the background must stay transparent.
How we checked this
Synthetic samples. No personal files. Results can vary with browser encoders.
Tested: · Chromium 149.0.7827.55
Download measurements and file hashes · Testing method
Sample files are free to reuse under CC0.
Renaming a file does not convert it
A PNG named photo.jpg is still a PNG. Some apps label files from the extension alone. Aftermath checks the contents of supported files and uses the detected format.
In our browser regression check, a PNG with a JPG name opened in the resizer, inspector, and image-to-PDF tool. The original bytes stayed unchanged. A form that requires JPG may still require a real JPG export.
Try the filename check with a sample
The sample below contains PNG bytes but downloads with a .jpg name. Open it in the image inspector. It should report PNG. Use the image converter to create a JPG when you need one.
Keep transparency only when you need it
JPG cannot keep transparency. A clear area becomes a solid background when you export to JPG. Preview the new copy against the background where it will appear.
If a form requires an opaque image, export a copy with the requested background. A white preview alone does not prove that the file has no transparent pixels.
Check the exported copy
Reopen the download. Check its format, pixel dimensions, file size, and appearance. PNG has no JPG-style quality slider; a detailed photo may need a different format or fewer pixels to become much smaller.
Desktop tools and commands
Use a local tool