Are my third parties green?
Check the third party resources used by a website.
What does this test check for?
Green hosting
Are third party resources being served from a host that is powered by renewable energy, or provides proof to support their green claims?
Data transfer
How much of your site's overall size comes from third party requests?
Effective caching
Are third party resources being cached effectively for repeat visitors/website navigation?
Carbon impact
What is the estimated carbon emissions resulting from third party resources on each page load?
Why does this matter?
The web's carbon footprint
It's estimated that global information and communication technology (ICT) accounts for around 4% of global CO2 emissions. That is about equivalent to Germany's national emissions (the world's 7th largest polluter), and is more polluting than the civil aviation sector.
Third party code is widespread
Over 94% of sites use at least one third-party resource, accounting for over 45% of website requests (2021 Web Almanac: Third Parties). That's a fair chunk of overall website traffic originating from shared, public origins.
Small changes, big impacts.
Serving these widely used scripts from green web hosts, and reducing their transfer size would be a huge step towards a greener web.
Shaving off a single kilobyte in a file that is being loaded on 2 million websites reduces CO2 emissions by an estimated 2950 kg per month.
How does it work?
This tool analyses the results on a URL testing with Google Lighthouse. It checks for requested resources that are served from third-party domains, and categorises them based on data from Patrick Hulce's third-party-web repository.
Resources served from subdomains are not considered third-party requests in this test.
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The Green Web Foundation's (GFW) dataset is used to determine if a third-party resource is hosted in a data center that uses green energy. Of course, the GWF database is not 100% perfect and also includes data centres that purchase standard grid electricity but offset their emissions. This tool does not differentiate in those cases.
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The Lighthouse test results calculates a 'cache hit probability' for resources that are served with short, or inefficient, caching policies. This test considers resources with a 'cache hit probability' of less than 50% to have ineffective caching.
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The estimate for carbon emissions leans heavily on the methodology outlined in Calculating Digital Emissions by Sustainable Web Design, with a few modifications:
- Assumes that the visitor is a brand new visitor so no cache is enabled.
- No adjustments are made for returning visitors.
- If the third-party resource is served from a green web host, then a 15% reduction is applied to CO2 emissions.
It is assumed that all websites use standard grid electricity for the telecoms network and end user, since we have no way to determine otherwise.
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The default test location is based in the US. It is possible to test on EU based servers by changing the "Test region" field in the Advance settings area under the test form.
Tests are run on page load, using an emulated desktop environment, without any cookies set. This means:
- Any third-party requests made after user interaction are not captureed.
- Third parties requested after a user opt-in action will not be captured.
Find out the impact of your site's third-party resources.
Test a web page