Knowledge
Improve Lighthouse scores through your images
On most WordPress sites, images are the biggest drag on your Lighthouse score. If you tackle the weight and format of images, you often gain the most points with the least effort.
In short
- Four of the most common image audits focus on weight and format
- Modern formats like WebP and AVIF significantly reduce your file size
- Spark handles exactly those audits automatically
The image audits that Lighthouse shows
Lighthouse mentions images in a handful of recurring recommendations. Each one points to the same underlying problem: images that are too large or delivered incorrectly.
- Properly size images: don't deliver a 3000px photo for a 600px spot
- Efficiently encode images: compress more without visible loss
- Serve images in next-gen formats: use WebP or AVIF
- Defer offscreen images: load images only when they come into view
How Spark tackles these points
Spark Media Optimizer compresses each file based on your profile and delivers WebP or AVIF where possible with a proper fallback for older browsers. This way you solve the audits for encoding and next-gen formats in one go.
Because the plugin works on your own server and serves the right format per browser, you improve your Largest Contentful Paint without becoming dependent on an external service.
Note: Lighthouse measures per page. Test your heaviest pages, not just your homepage, because that's usually where the biggest gains are.
Solve your toughest Lighthouse points in one run.
Frequently asked questions
Images are one factor. Spark handles the image audits, but your overall score also depends on scripts, CSS, and your server. However, images are often the quickest win.
No. Spark scans your existing media library and processes the images that are already there, so you don't need to re-upload anything manually.
Lazy loading delays loading, but doesn't change the file size. Spark reduces the file itself, so the image that does load is actually lighter.