Five qualities, one photo
The table converts one 2000 x 1333 JPEG, 694 KB in size, at five WebP qualities. Quality 60 gave 135 KB, which is 81% smaller. Quality 90 gave 583 KB, 16% smaller, at 40.6 dB, close to the original pixels.
Most of that saving comes from the source being a very high quality JPEG. Compare it with simply recompressing the same JPEG: at quality 80 that gave 274 KB and 36.2 dB. WebP at quality 78 gave 274 KB and 36.1 dB. On this photo the two are close to a tie. WebP's edge over a well-tuned JPEG encoder is modest on this photo.
| WebP quality | Size | Smaller than the JPEG | Fidelity (PSNR) | Time |
|---|---|---|---|---|
| 60 | 135 KB | 81% smaller | 34.3 dB | 390 ms |
| 70 | 191 KB | 73% smaller | 35.0 dB | 443 ms |
| 78 | 274 KB | 61% smaller | 36.1 dB | 458 ms |
| 85 | 415 KB | 40% smaller | 38.4 dB | 473 ms |
| 90 | 583 KB | 16% smaller | 40.6 dB | 509 ms |
The source JPEG is a high quality export, so much of the saving here comes from dropping its excess detail. Quality numbers are not comparable across formats; the PSNR column shows how close each result is to the original pixels. Test images are synthetic files made by this project: a 2000 x 1333 landscape photo, a 1600 x 900 interface screenshot and a 1200 x 1200 transparent illustration. Timings: one thread of WebAssembly on Node v22.23.4, Intel(R) Xeon(R) Processor @ 2.10GHz, 2 cores, measured 2026-10-31. Other devices will differ.
When the conversion is worth it
A photo exported at high quality has a lot to give up, so the saving is large. A photo that came from a phone at moderate quality has less to give, and you may see a small gain or none. The result line shows the exact numbers for your file, including when WebP comes out larger, so you can keep whichever is smaller.
WebP also does things JPEG cannot, such as transparency and lossless storage. If you want those, the choice is easy.
A quality guide
- Around 90 for a result close to the source. In the test that was 40.6 dB.
- Between 78 and 85 for normal web photos.
- Around 60 to 70 for thumbnails and previews. Quality 60 gave 135 KB for the full-size photo.
Quality numbers do not line up between formats, so judge by the compare view rather than by the number.
Orientation and metadata
Photos are rotated to match their orientation before encoding, so a portrait shot stays upright. Camera details and GPS location are removed by default, and only the colour profile and the author can be kept. The EXIF viewer shows what a file contains before you decide.
Before you replace files on a site
- Compare the original and the WebP at 100% zoom, not only in a thumbnail.
- Read the result line. If the WebP is larger, keep the JPEG.
- Keep the original JPEG somewhere safe. A converted file cannot be turned back into it.
- Test the files where they will be used, such as your CMS, email templates and social previews.
Use File names in Advanced settings to add the pixel width to each name, for example {name}-{width}, so files of different sizes do not overwrite each other.
Questions
Does converting a JPEG to WebP lose quality?
Yes, a little. The JPEG is decoded and encoded again, and both formats are lossy. At quality 85 to 90 the difference is small.
Why is my WebP larger than the JPEG?
The JPEG may already be compressed hard. Lower the WebP quality, or keep the JPEG.
Can I hit a size instead of a quality?
Yes. Turn on a target size in Advanced settings, under File size.
Do browsers support WebP?
Every current major browser does. Some older apps do not, so test where you plan to use the file.