Short answer: WebP is an image format from Google with lossy and lossless compression. Lossy WebP images are 25% to 34% smaller than comparable JPEGs at equivalent quality, and lossless ones are 26% smaller than PNGs. Major browsers and Google Search support it.
How WebP compares with JPEG, PNG and GIF
Google measured the savings against the formats WebP replaces, and web.dev recommends it as a replacement for JPEG, PNG and GIF images.
| Case | What Google measured | Use it for |
|---|---|---|
| Lossy WebP | 25% to 34% smaller than comparable JPEGs at equivalent quality | Photos |
| Lossless WebP | 26% smaller than PNGs | Graphics where every pixel has to stay |
| Transparency | 22% more bytes in lossless; lossy usually about 3 times smaller than PNG | Logos and cut-out images |
| Animation | Can be smaller than GIF and APNG | Short animated images |
| Google Search | Supported in the src attribute of an img tag, like BMP, GIF, JPEG, PNG, SVG and AVIF | Any image you want found in Google Images |
From Google for Developers, “An image format for the Web”, and Google Search Central, “Google image SEO best practices”, read November 3, 2026.
How WebP makes images smaller
Lossy WebP uses predictive coding, the method the VP8 video codec uses for keyframes: it predicts each block of pixels from its neighbors and stores only the difference.
Lossless WebP rebuilds new pixels from image fragments it has already seen, and it can use a local palette when it finds no useful match.
What large sites saw
web.dev says WebP files are usually 25% to 35% smaller than their JPEG and PNG versions. YouTube found that WebP thumbnails made pages load 10% faster.
Facebook saw files shrink by 25% to 35% for JPEGs and by 80% for PNGs when it switched to WebP. You can measure the change in PageSpeed Insights, and our PageSpeed Insights guide shows where to look.
How to move your images to WebP
- Start with the largest photos on the pages that matter most.
- Convert them with the cwebp command-line tool, or with the Imagemin WebP plugin if your site uses build scripts.
- Try a few quality levels between 0 and 100 and keep the lowest that still looks right.
- Use lossless WebP for graphics where every pixel has to stay.
- If you still support older browsers, use a picture element with a JPEG or PNG fallback.
- Keep each file’s extension matching its type.
- Test the page in PageSpeed Insights before and after the change.
Our guides to lazy loading images and alt text cover the other half of image SEO.
How we use WebP on our own site
Our WordPress media library held 596 images on November 3: 565 in WebP, 15 in PNG, 10 in JPEG and 6 in SVG. That puts 95% of our images in WebP.
Every guide photo goes up as WebP. The 77 header photos, at 2400 by 1050 pixels, average about 156 KB, and the largest is 315 KB. Their 1200 by 630 versions for sharing average about 55 KB.
We keep the original of each photo, so we can convert it again at another quality without losing detail.
Before you switch an image to WebP
- You kept the original file.
- The quality level looks right on a phone and a computer.
- Graphics with sharp edges use lossless WebP.
- The file extension matches the type.
- Older browsers get a fallback, if you need them.
- The page loads faster in PageSpeed Insights.
RememberWebP gives the same photo in a smaller file, and Google Search reads it like any other image. Start with your largest photos, keep the originals and measure the page when you’re done.
If you want a faster site with images that load well on phones, see our web design service.
Quick answers about WebP
Does Google index WebP images?
Yes. Google Search supports images in the src attribute of an img tag in BMP, GIF, JPEG, PNG, WebP, SVG and AVIF. Google also suggests that the file extension matches the file type.
Do all browsers support WebP?
Google says WebP is supported natively in major browsers such as Chrome, Safari, Firefox, Edge and Opera. If you still need older browsers, web.dev suggests a picture element that serves WebP with a JPEG or PNG fallback.
Can WebP images have a transparent background?
Yes. Lossless WebP supports transparency for just 22% more bytes, and lossy WebP supports it too, usually at about a third of the size of the same image as a PNG.
What quality setting should I use?
web.dev says quality is usually the only setting you need, on a scale from 0, the worst, to 100, the best. Try a few levels on your own photos and keep the lowest one that still looks right.
Does converting to WebP lower image quality?
Not with lossless WebP, where no data is lost. Lossy WebP makes files smaller and can lower quality, which is why the quality setting matters. Keep the originals so you can convert again.
Sources
Read on November 3, 2026. Google for Developers: An image format for the Web. web.dev: Use WebP images. Google Search Central: Google image SEO best practices. Our own case: our WordPress media library, November 3, 2026.