How efficient is the code of your website in regards to sustainability?


How do we determine if a website is performing in terms of CO2 emissions? How do we make this clear to our users?

This has been on our mind since we started Zifera. The first type of metric we used was based on how you performed compared to others who had used (Zifera's main inspiration). We decided to remove this metric because we are not sure it gives the most unbiased results. Maybe people who use this tool are more likely to have a well optimised website compared to the average website.

That's why decided to add two new metrics:

- How do you perform compared to the average website size (as calculated by httparchive) who run a yearly analyses of the web). For example, emits 91% less energy than the average website.
- Code efficiency rating. How well optimised is the code of your website? Are any kilobytes wasted by using wrong image sizes or added a lot of unused javascript? Having a low efficiency rating means you can lower your website's emissions simply by optimising your code.

It's possible to have a website that emits much more CO2 than average, but still have a 100% efficiency rating. This means you need to make design changes. Maybe you are using a lot of videos? Can you replace images by using vector illustrations?

Test your website at

Want to make your website climate neutral?
Try Zifera 14 days for free.