JPG to WebP and Core Web Vitals
Largest Contentful Paint (LCP) is the Core Web Vital that measures how long the biggest thing on screen takes to appear. On most pages that's a photo: a hero banner, a product shot or a featured image. Google's target is an LCP of 2.5 seconds or less, and a heavy JPG is one of the most common reasons pages miss it.
Converting JPG to WebP is a quick win because WebP compresses photos more efficiently. Google reports that lossy WebP files are 25–34% smaller than comparable JPEGs. The same photo, fewer bytes, a faster LCP. PageSpeed Insights and Lighthouse flag this directly with "Serve images in next-gen formats".
Format alone won't fix a slow page, but it's one of the few changes that needs no code: convert, re-upload, done.
Choosing a WebP quality
WebP and JPEG quality numbers aren't directly comparable, so trust your eyes and the file size rather than a fixed number. A practical routine:
Remember that the original JPG is already lossy. Converting it to WebP compresses it a second time, so start from the highest-quality JPG you have, ideally the camera original or a fresh export, rather than a copy you downloaded from a website.
- Start at High (90%). For most photos it looks identical to the JPG and is already smaller.
- Step down to Med (75%) for large background images, where small detail matters less.
- Zoom in on faces, text and fine textures in the preview. If they look smeared, go back up.
- Resize first. A 6000 px camera photo shown at 1200 px wide wastes far more bytes than the format does. Use the Image Resizer, then convert.
Is WebP safe to use everywhere?
On the web, yes. Chrome, Edge, Firefox and Safari all display WebP, and WordPress, Shopify, Wix and Squarespace accept WebP uploads. The exceptions are outside the browser: some email clients, older desktop apps and print services still expect JPG. Keep your original JPEG for those and use the WebP on your site.
| Where the image goes | Use |
|---|---|
| Website, blog, online store | WebP |
| Email newsletters | JPG |
| Printing | JPG at high quality |
| Social media uploads | JPG (platforms re-compress anyway) |
