JPG or WebP for an online form?
The destination’s accepted formats come first. A smaller file is not useful if the website cannot accept that format.
Start with the accepted file types
If a form says JPG or JPEG, choose JPG in SizeKit. The extensions .jpg and .jpeg refer to the same image format. If a form explicitly accepts WebP, you can try a WebP export and compare its quality and size with a JPG version.
Do not assume a website accepts a format just because your browser displays it. Upload systems may restrict formats independently of browser support.
| Your requirement | Choice | Check before submitting |
|---|---|---|
| Form requests JPG/JPEG | JPG | Dimensions, size range and visual clarity. |
| Transparency is needed and WebP is accepted | WebP | Transparent areas remain correct in the download. |
| Form requires PNG output | Another tool | SizeKit accepts PNG input but does not export PNG. |
| Either JPG or WebP is accepted | Compare both | Use the result that meets the rules with adequate detail. |
What happens to a transparent background?
JPG has no transparent pixels. SizeKit places a white background behind transparent areas when exporting JPG. This is useful when you want a white background, but it can change the appearance of logos and graphics.
WebP can preserve transparency. In SizeKit, choose WebP when transparency matters and the destination accepts it. This preserves existing transparent areas; it does not remove a background from an ordinary photo.
Will WebP always make a smaller file?
No single format wins for every image and setting. SizeKit tries to fit your selected format under your chosen limit, keeping the dimensions fixed. Compare the downloaded outputs at the same dimensions. Look particularly at edges, text and fine facial details rather than judging only the file size.
Both output paths can use lossy compression. A stricter size limit can produce more visible artifacts. A very small image with many sharp lines may not remain readable under the limit even when it technically fits.
Changing the extension is not conversion
Renaming photo.webp to photo.jpg leaves the file’s encoding unchanged. A form may reject it because its contents do not match the extension. To convert it, open the file in SizeKit, select JPG, process it and download the new file ending in .jpg.
Keep your original. Exporting the same source to another format is preferable to converting a succession of already compressed copies.
Inputs and outputs SizeKit supports
You can open JPG, PNG or WebP images up to 20 MB and 40 megapixels. Output dimensions can range from 1 to 4096 pixels on either side. Files export as JPG or WebP; animated images become a still frame. HEIC, PDF and PNG output are not supported.
If your browser cannot encode WebP, the tool asks you to choose JPG. You still need to confirm that JPG meets your destination’s requirements.
Compare JPG and WebP exports