Start with where the image will go
A good export is the one your next app accepts at the quality you need. Check a submission form or publishing system before converting. A smaller file is not useful if the recipient cannot open it. Keep an untouched original and make a separate delivery copy, especially when an image will be edited again.
For a photo-heavy page, compare JPG and WebP. For a screenshot containing small text, or a graphic that must retain transparent edges, start with PNG. These are starting points, not promises that one format always produces the smallest file.
Decide whether transparency matters
PNG supports transparency. WebP can also store transparent pixels, while ordinary JPG does not. A logo placed over different backgrounds needs more than a white rectangle that looks transparent on a white page. Inspect the edges against the background where you will actually use it.
Converting a transparent image to JPG flattens it onto a background. Check that background in the exported file. Converting the JPG back to PNG will not recreate the removed transparency; return to your original transparent file instead.
Separate compression from recovering detail
JPG normally uses lossy compression: reducing its quality can discard detail. PNG uses lossless compression, but saving a previously damaged JPG as PNG does not undo that damage. WebP supports both lossy and lossless encoding; the format alone does not tell you which mode a particular tool uses.
The asdftools WebP and image compression controls use browser encoding with a quality setting, not a dedicated lossless WebP mode. Compare thin text, hair, gradients and high-contrast edges. Repeatedly editing and exporting an already compressed image can compound visible defects.
Change one setting at a time
First decide the pixel dimensions needed for the destination. A very large photograph may not need its full dimensions in an email or a small web card. Use Resize image for that change, then try compression on the resized copy. Do not enlarge a small original expecting new detail.
Begin with a moderate quality setting and inspect the downloaded result at its intended display size. Lower quality in small steps if necessary. Quality values are not a guarantee of a specific file size, and an export can be larger than its source.
Check the actual exported file
Open the download before replacing or sharing anything. Browser re-encoding is not an archival workflow: original metadata, color profiles and animation are not guaranteed to survive. These converters are for still images, not preserving animated sequences or a professional color-managed master.
- Confirm the destination accepts the selected file format.
- Compare dimensions, file size, orientation, sharpness and transparent edges.
- Keep your original and name the exported copy clearly.