Why WebP files end up needing conversion
Saving an image from a modern website often produces a .webp file, because many sites serve WebP to browsers that announce support for it. The file then fails to attach to an older email client, a print shop form or a document editor that only knows JPG. This converter decodes the WebP with the browser, fills a same-size canvas with solid white, draws the image over it, and re-encodes as JPEG with your quality value (10% to 100%, default 90%).
What is distinctive about this direction
You are moving between two lossy formats, so the quality cost compounds. The WebP was already compressed with VP8-style prediction. The JPG step quantises DCT blocks on top of that, which means two different sets of artefacts can overlap. In practice, 90% is a safe default; going below about 80% tends to show smudging on faces and text that the WebP alone did not have. File size usually goes up, because WebP is typically smaller than JPG at comparable visual quality (Google's own comparisons suggest 25 to 34%, though results vary by image).
Transparency is the other difference. A WebP can carry an alpha channel even when it is lossy, but JPG cannot. Transparent pixels become white, and soft edges blend toward white rather than toward the page colour they were designed for. There is no background colour picker on this page, so if you need a non-white fill, add it in an editor before converting.
Worked example
A 1200×800 product shot saved from a shop site is 64 KB as WebP. Converted at 90% it might come out around 110 to 160 KB. At 70% it may land near 70 KB, close to the original size, but with visible softness on fine textures. The pixel dimensions stay at 1200×800 in every case, and the file keeps your original name with a .jpg extension.
| WebP feature | What happens in the JPG |
|---|---|
| Alpha transparency | Flattened onto white |
| Animation | Only the first frame is converted |
| Lossless WebP source | Becomes lossy, so choose 90% or above |
| Embedded colour profile | Not written to the output file |
Common mistakes
- Converting transparent stickers or logos. They arrive with a white box. Use WebP to PNG to keep the see-through areas.
- Expecting animation to survive. JPG is a single-frame format; an animated WebP gives you just one still.
- Assuming a small file stays small. If the size matters, run the result through the Image Compressor or lower the pixel size with the Image Resizer.