Start with the image, not the extension
Photographs contain many gradual color changes. Lossy formats can reduce their size by simplifying detail, but repeated saves can make edges and textures look rough.
Screenshots, logos, and diagrams often contain flat fills and small text. Lossless PNG can preserve hard edges better, though photographs saved as PNG can be much larger.
Check transparency
JPEG has no alpha transparency. If the source has transparent pixels, a JPEG export needs a background color.
PNG supports transparency. WebP also supports transparency in browsers and software that decode it, but check the target environment before choosing it.
Use WebP when the destination supports it
WebP supports lossy and lossless encoding in the format itself. This site passes a quality value to the browser's WebP encoder; it does not expose a separate lossless toggle. PNG ignores the quality control.
An exported file can be larger than the source. Compare actual bytes and inspect the visual result at the size where it will appear.
Common questions
Should I convert every image to WebP?
No. Keep a format that suits the image and destination. Compatibility, transparency, downstream editing, and file size all matter.
Can I convert a vector logo to WebP here?
This version focuses on browser-decodable raster images. The converter does not offer an SVG editing workflow.
References
Sources explain browser behavior or guidance; they do not verify a particular output file.