Compressing your images: Crawl Audit check 80

Short answer: a photo straight off a camera or design tool is often several times bigger than it needs to be. Compressing it keeps it looking the same and makes it load faster. Check 80 warns when PageSpeed finds images that could be meaningfully smaller.

What Crawl Audit checks

• Full report: PageSpeed's image audit. If it lists images worth compressing, the check warns and shows the possible saving.
• Free check: Crawl Audit can't measure image files without PageSpeed, so it passes with "No oversized images detected in markup."
• Pass: no images, or nothing worth compressing. Warning: savings found.

What Google says

• Lighthouse's older audit re-saved JPEG and BMP images at quality 85 and flagged any that would shrink by 4 KiB or more.
• In Lighthouse 13 this moved into the "Improve image delivery" insight: "Any images with estimated byte savings less than 4 KiB won't be flagged."
• "Most image formats support a compression level that can be tuned to improve the image file size at the cost of image quality."

How to compress yours

• Resize first. A 4,000-pixel photo shown 800 pixels wide is wasted bytes, however well it's compressed.
• Then compress. Lighthouse's own test re-saves photos at quality 85 to see what could be saved.
• Use a modern format where you can (check 79).

On your platform

• Shopify, Wix and Squarespace: Wix compresses images, Squarespace makes up to seven sizes of each upload, and Shopify serves modern formats. Uploading a sensible size still helps.
• WordPress creates smaller sizes of each upload. An image optimisation plugin can compress them further.
• Next.js: next/image resizes and compresses on request, at quality 75 by default.

Sources

• Chrome for Developers, Efficiently encode images and Improve image delivery (8 October 2025), checked 3 October 2026.