Efficiently encode images
Google Lighthouse will scan all the JPG and PNG images of your website. The tool will process them with a compression level of 85%, and then these optimized images will be compared with your original ones.
If during this comparison, they discover a potential saving bigger than 4kb, that image will be listed as “optimizable” and it will trigger this recommendation.
You can read more about it here: https://web.dev/uses-optimized-images/
This should be considered as a high priority optimization. It can have a significant impact on the overall performance, especially when the potential KB savings are high.
Why does this happen?
In many cases, while building a website we use images that are not fully optimized. For example, when building a website with WordPress, it is very common to upload raw images with a high resolution using the media manager, and these images might end up being used in posts and themes.
How to fix this?
Heads up! WP Rocket cannot fix this for you, but you can address it with other tools
This is something that has to be fixed by each website owner. As a general rule, it is always recommended to optimize your images before adding them to your website. This can’t be done inside WP Rocket, but here you have some general tips on how to tackle this recommendation:
- Check the images listed on the report and compress them using an optimization tool.
- Enable WP Rocket Lazyload, please note it won’t optimize the images but it might help.
- Serve images with the correct dimensions.
- Use our service, Imagify, and its WordPress plugin to automate this process and optimize all your existing images with one click: https://imagify.io/wordpress/. As a very important bonus, Imagify can also convert your images to WebP format
You may also be interested in our blog post on image optimization: