Check if your images use modern formats

SiteCurl checks each <img> tag on your page and looks at the file type. Shots using old formats (JPEG, PNG, GIF, BMP, TIFF) are flagged. Shots using modern formats (WebP, AVIF, SVG) or served through a <picture> tag with a modern source pass the check.

The check is smart about edge cases. Data URIs (inline shots) are skipped. Shots inside a <picture> tag that includes a WebP or AVIF source are not flagged, even if the fallback <img> uses JPEG. CDN URLs with no file type are also skipped since the real format cannot be told from the URL alone.

For each flagged shot, SiteCurl shows the source URL so you know which files to convert. On a full scan of 100 pages, this covers each visible image across your site.

JPEG was made in 1992. PNG came in 1996. Both are still widely used, but they are not lean by modern standards. WebP, built by Google, makes files 25-35% smaller than JPEG at the same visual grade. AVIF, based on the AV1 video codec, can be 50% smaller. The gap is not visible to the eye in most cases.

The math matters since images are the largest files on most web pages. A typical page loads 1-5 MB of image data. If those were 30% smaller, the page would save 300 KB to 1.5 MB. On a slow mobile link at 1 Mbps, that is 2-12 seconds of load time saved.

Browser support for WebP is now total. Each modern browser (Chrome, Firefox, Safari, Edge) supports it. AVIF support is newer but covers Chrome, Firefox, and Safari 16.4+. The <picture> tag lets you serve AVIF to browsers that support it and fall back to WebP or JPEG for older ones.

Most CDNs and image tools (Cloudinary, imgix, Cloudflare) can convert shots on the fly. You upload a JPEG, and the CDN serves WebP or AVIF based on what the browser accepts. No manual work needed.

Images are often the heaviest part of any web page. Switching from JPEG/PNG to WebP can cut total page weight by 20-30% with no visible loss. That leads directly to faster load times, lower bandwidth costs, and better scores on Google's speed tests.

Faster pages get more clicks and reads. Studies show that each extra second of load time raises bounce rate by 5-10%. For image-heavy pages (portfolios, product listings, galleries), format gains have the largest impact of any single speed fix.

Page speed is a confirmed Google ranking factor. Lighthouse checks for modern image formats and flags old ones. Fixing this issue directly lifts your Lighthouse speed score.

Online stores with product photos gain the most. A product page with 10 high-grade JPEG shots at 200 KB each loads 2 MB. Switching to WebP drops that to roughly 1.3 MB. Across 20 product pages in one visit, the savings add up to megabytes.

Portfolio and photo sites face a tension between image grade and speed. Modern formats solve it: AVIF delivers sharp output at file sizes that load fast even on mobile.

Bloggers who use stock photos or screenshots in their posts often have the easiest path. Most image editors and online tools now export to WebP with one click.

Step 1: Find old-format shots. Run a SiteCurl scan. The image format result lists how many use old formats and shows example URLs. These are the files to convert.

Step 2: Convert to WebP. Use a tool like Squoosh (squoosh.app), ImageMagick, or your editor's 'Export As' option. Set grade to 80 for photos (looks the same as JPEG at 85). For batch work: cwebp -q 80 image.jpg -o image.webp.

Step 3: Use the picture tag for fallbacks. Wrap shots in a <picture> tag to serve WebP with a JPEG fallback: <picture><source srcset="image.webp" type="image/webp"><img src="image.jpg" alt="Description"></picture>. This way, older browsers still see the image.

Step 4: Set up auto conversion. If you use a CDN like Cloudflare, turn on Polish (image tuning) in your dashboard. Tools like Cloudinary and imgix convert on the fly based on the browser's Accept header. This cuts out manual work fully.

Step 5: Check your CMS plugins. WordPress has plugins like ShortPixel and Imagify that convert on upload. Shopify's CDN serves WebP on its own for most image URLs. Check what your platform offers before building a manual flow.

Not checking output grade. Always compare the old and new image side by side. At very low settings, WebP can show marks around text and edges. Use grade 75-80 for photos and grade 85-90 for shots with text.

Serving WebP with no fallback. While WebP browser support is now total, some email clients and older apps do not support it. Use the <picture> tag to add a JPEG fallback for the widest reach.

Missing CSS background shots. Shots set via background-image in CSS are not checked by this scan, but they should also be converted. Use CSS feature queries or multiple backgrounds to serve modern formats in stylesheets.

Re-encoding shots that are already small. Converting a heavily shrunk JPEG to WebP does not always help. If the JPEG is already at grade 60, the WebP may not save much. Start from the highest grade source you have for the best results.

After converting, run a new SiteCurl scan. The old-format count should drop to zero. You can also check in browser dev tools: open the Network tab, reload the page, and filter by 'Img.' The Type column shows the MIME type. Look for image/webp or image/avif instead of image/jpeg or image/png.

Compare total image bytes before and after. The Network tab shows total transfer size at the bottom. A 20-30% drop in image bytes confirms the switch is working.

Modern image formats deliver the same visual grade in smaller files. WebP is backed by all browsers and saves 25-35% over JPEG. AVIF saves even more. Switching your shots is one of the highest-impact speed gains you can make, and most CDNs can do it on their own.