Best Image Format for Google PageSpeed in 2025
Google PageSpeed Insights and Lighthouse both audit your images and flag JPG and PNG as failing the 'Serve images in next-gen formats' check. The fix is straightforward: convert to WebP (safe for all modern browsers) or AVIF (highest performance, slightly less universal). This guide covers exactly what PageSpeed wants and how to deliver it.
Quick Answer
Google PageSpeed Insights and Lighthouse both audit your images and flag JPG and PNG as failing the 'Serve images in next-gen formats' check. The fix is straightforward: convert to WebP (safe for all modern browsers) or AVIF (highest performance, slightly less universal).
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Step-by-Step Guide
5 steps · takes under 1 minute
Run PageSpeed to identify failing images
Go to pagespeed.web.dev, enter your URL, and run the analysis. Under 'Opportunities', look for 'Serve images in next-gen formats' — this lists every image on your page that should be converted to WebP or AVIF, with the estimated savings.
Convert all listed images to WebP
Download the images listed in the PageSpeed audit. Drag them into the Format Converter. Select WebP output at 80–85% quality. Download the converted files. Upload them to your server in place of the originals (or with added .webp extension).
Update your HTML or CMS
Replace <img src='photo.jpg'> with <picture><source srcset='photo.webp' type='image/webp'><img src='photo.jpg'></picture>. Or update the src attributes directly to .webp if you're comfortable dropping JPG fallback (safe for all sites built after 2022).
Also check 'Properly size images'
PageSpeed often flags this alongside format issues. It means your image pixel dimensions are larger than the display size. Resize images to their display dimensions using the Resize tool.
Re-run PageSpeed to verify improvement
After changes, wait 1–2 minutes and re-run PageSpeed. The 'Serve images in next-gen formats' opportunity should show 0 issues or significantly reduced savings estimates.
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ImgToolkit runs entirely in your browser using the Canvas API. Your images are never sent to a server, never stored in the cloud, and never seen by anyone else. This makes it safe for sensitive documents, client work, medical imagery, and confidential screenshots.
Pro tip
Pre-optimizing images before uploading to a platform gives you more control than relying on the platform's automatic (and often aggressive) compression.
Format & File Size Comparison
Same 1080×1080px photo processed four ways
| Format | Quality | File Size | Notes |
|---|---|---|---|
| PNG (original) | Perfect | 4.2 MB | No compression — too large for web |
| Compressed PNG | Visually identical | 1.1 MB | −74% — transparency preserved |
| JPG (85% quality) | Excellent | 310 KB | −93% · Best for photos |
| WebP (85%)BEST | Excellent | 205 KB | −95% · Recommended for web |
Based on a 1080×1080px photo. Results vary by image content and complexity.
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