Improve PageSpeed Insights with media optimization
Measurable results
Which PageSpeed warnings relate to images
Step-by-step plan: from warning to green score
Open the report and note which image audits are failing
Convert to next-gen formats where requested
Serve images at the correct display size
Lazy load offscreen images, except for your LCP image
Repeat the test and compare
Formats and their impact on PageSpeed audits
| Approach | Typical savings | Helps most with |
|---|---|---|
| AVIF | Often the largest savings; in our tests up to 94% smaller than the original. | "Serve images in next-gen formats" and "Efficiently encode images". |
| WebP | Substantial savings with broad support; usually 25 to 50 percent smaller than JPEG. | "Serve images in next-gen formats" as broad fallback. |
| Serve correct size | Varies greatly depending on the situation; often the quickest win with an oversized hero image. | "Properly size images". |
| Lazy loading (non-LCP) | No savings in bytes, but in initial load time. | "Defer offscreen images". |
Common pitfalls when chasing a green score
- Also lazy loading your LCP image, which actually slows down the initial render instead of speeding it up.
- Only optimizing the hero image and forgetting the rest of the page.
- Using a standalone optimization tool that doesn't work with your cache plugin, so visitors still see the old files.
- Only looking at the number without checking actual load time and user experience.
- Not doing a separate mobile test; PageSpeed Insights shows desktop and mobile separately, and mobile usually scores lower.
Frequently asked questions
No. Images are just one of the factors that PageSpeed measures; server response time, JavaScript, fonts, and external scripts also count. Optimizing images specifically addresses the image audits, but doesn't necessarily fix all other issues.
Lighthouse is the underlying auditing engine; PageSpeed Insights is an online tool that uses Lighthouse and can also display real field data from Chrome users.
Yes, you can compress it, but make sure that image doesn't load lazily. A smaller, directly loaded LCP image is usually the quickest win for that specific measurement.
That's usually a caching issue: your hosting cache, a cache plugin, or a CDN is showing a previously stored version. Purging the cache after a bulk run usually solves this.
Yes, the underlying files become smaller for all devices. Mobile often scores lower than desktop, simply because the measurement simulates a slower connection.
After major changes to content, theme, or plugins, a new measurement is advisable. Individual measurements can also fluctuate somewhat, so a single measurement isn't always representative.