WebP vs JPEG: Differences, File Size and When to Use Each

JPEG has been the standard format for photographs since the early 1990s. WebP, developed by Google, is newer and was designed for the web. For most website photos WebP is the more efficient choice, but JPEG still has advantages. Here is a practical comparison.

At a glance

File size

Google's WebP documentation states that lossy WebP images are 25 to 34% smaller than comparable JPEG images at equivalent quality, measured with the SSIM index. That is an average from Google's tests. In practice the saving depends on the photo and the encoder settings, and a JPEG that has already been heavily compressed may not shrink much, or may even grow, when converted at a high quality setting.

The way to know is to convert a few of your own images and compare sizes and appearance. Image York's JPG to WebP converter shows the size of each result.

Quality

At high quality settings, both formats look the same as the original at normal viewing sizes. The differences appear when you compress hard. JPEG tends to show 8 x 8 pixel blocks and ringing around edges. WebP tends to blur fine detail instead, which many people find less objectionable. Neither format is magic: low quality looks low quality.

Note that converting an existing JPEG to WebP cannot improve it. The WebP stores what the JPEG decoded to, artifacts included.

Compatibility

JPEG opens everywhere: every browser, phone, printer, email client and upload form. WebP is supported by all current major browsers and most content systems, but some older desktop programs and some forms still reject it. For files you send to other people, JPEG is the safer choice. For images on your own website, WebP is widely safe, and the <picture> element lets you provide a JPEG fallback if you need one.

Does WebP help SEO?

Indirectly. Smaller images help pages load faster, which can improve Largest Contentful Paint, one of Google's Core Web Vitals. Search rankings depend mostly on content and relevance, though, and resizing oversized images usually saves far more than switching formats. See the guide to images and Core Web Vitals for the fixes that matter most.

Which should you use?

• Photos on your website: WebP, at a size that matches your layout.
• Photos you email, print or upload to forms: JPEG.
• Images with transparency: WebP or PNG, never JPEG.
• Archiving originals: keep the camera originals as they are.