How JPG to WebP Conversion Improves Your PageSpeed Score

Run Google PageSpeed Insights on almost any site and you will likely see the same warning: "Serve images in next-gen formats." The fix it is asking for is almost always converting your JPG (and PNG) images to WebP.

This post explains exactly what that warning means, how much it actually helps your score, and the fastest way to convert your images without any software installation.

What "Serve Images in Next-Gen Formats" Actually Means

Google PageSpeed Insights grades your page on a 0–100 scale. The "Serve images in next-gen formats" item is an opportunity — not a failing grade on its own — but it directly affects two things that do affect your score:

• LCP (Largest Contentful Paint): If your hero image or a large above-the-fold image is a JPG, converting it to WebP reduces its download time, which typically improves LCP.
• Total Blocking Time / bandwidth: Smaller images mean faster page load overall, especially on mobile connections.

WebP is the format Google recommends because it is the most widely supported next-gen format. AVIF is technically better compressed but has less browser coverage. For most sites, WebP is the right call.

How Much Smaller Is WebP vs JPG? Real Numbers

Google's own data shows WebP images are typically 25–35% smaller than comparable JPGs at the same visual quality. For photos with complex detail (product shots, lifestyle images), the savings are toward the high end of that range.

What this means in practice:

• A 300 KB hero JPG becomes roughly 190–225 KB as WebP
• A page with 10 product JPGs averaging 150 KB each saves roughly 375–525 KB total
• On a 3G connection that difference is 2–4 extra seconds of load time

PageSpeed Insights will actually show you the estimated savings for your specific images once you run it — look at the "Opportunity" column next to the warning.

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Step-by-Step: Convert Your JPGs to WebP and Update Your Site

Step 1 — Convert your images. Use the free browser converter on this page. Drop in your JPG, adjust the quality slider (80–85 is the standard recommendation for web use), and download the WebP file. No software to install, nothing uploaded to a server.

Step 2 — Replace the image files. Upload the new .webp files to wherever you host your images — your media library, CDN bucket, or /images folder.

Step 3 — Update your HTML or CMS.

• WordPress: Most modern themes and page builders accept WebP. Upload through Media Library and swap the image in each post/page. Alternatively, a caching plugin like WP Rocket or Imagify can auto-serve WebP versions.
• Shopify: Upload directly to Files. Update product images or theme image references to point to the new file.
• Raw HTML: Change <img src="photo.jpg"> to <img src="photo.webp">. For maximum compatibility, wrap in a <picture> element with a JPG fallback.

Step 4 — Re-run PageSpeed. The warning should disappear or the savings estimate should drop significantly for the images you converted.

The Safe Way: Using the <picture> Element as Fallback

WebP is supported in all major browsers as of 2023 — Chrome, Firefox, Safari, Edge. However, if you need to support very old Safari (pre-2020) or older Edge, the <picture> element lets you serve WebP to modern browsers and JPG as fallback:

<picture>
  <source srcset="photo.webp" type="image/webp">
  <img src="photo.jpg" alt="Product photo">
</picture>

For most sites in 2026, this is optional — plain <img src="photo.webp"> works fine. But if your analytics show a meaningful share of traffic from older devices, the picture element is the safe bet.

When Converting to WebP Is Not Worth the Effort

WebP gives you the biggest gain when:

• Your images are large (above 100 KB each)
• Images are above the fold — especially hero images that affect LCP
• Your site is image-heavy (ecommerce, photography, food blogs)

It is less impactful when:

• Your images are already small thumbnails
• You are already using a CDN that auto-converts images (Cloudflare Image Optimization, Imgix, Cloudinary)
• The PageSpeed opportunity estimate shows under 50 KB total savings — at that point other optimizations (lazy loading, script cleanup) will move your score more

The bottom line: if PageSpeed is flagging it and the savings estimate is over 100 KB, convert those images. It is one of the fastest wins available.

Frequently Asked Questions

Will converting to WebP hurt my SEO?

No — Google fully indexes WebP images and they appear in image search the same as JPG. The conversion typically helps SEO by improving Core Web Vitals scores, which are a ranking signal.

What quality setting should I use for web images?

80–85 is the standard recommendation. It is visually indistinguishable from 100 for most images but significantly reduces file size. Go lower (70–75) for images that are clearly compressed or not the main visual focus.

Does Google PageSpeed automatically convert images to WebP?

No — PageSpeed Insights only reports the opportunity. You need to convert the images yourself or use a CDN or plugin that handles the conversion automatically.

Can I batch convert all my JPGs at once?

The browser tool supports multiple files at once. Drop in several JPGs, convert, and download each WebP file. For very large batches (hundreds of images), a command-line tool or CDN auto-conversion is more practical.