How green is your website, and how would you know?
Sources last checked 2026-10-11 · next check 2027-07-11, in case anything has quietly stopped being true
A green website audit runs five checks: whether the site's hosting runs on verified renewable electricity, how much carbon each page view produces, whether every other server the page loads content from is green-hosted too, and whether the site publishes a valid carbon.txt file and a statement about its own environmental impact. The checks are automated and take minutes, and most of what they find can be fixed by the hosting provider, a developer or whoever writes the site's pages.
What the audit checks
Hosting and carbon
- Green hosting. Green hosting means the data centre that serves the site runs on renewable electricity, or buys an equivalent amount. The audit looks the host up in the Green Web Foundation directory, a public list of hosts that have shown evidence of it.
- Carbon per page view. An estimate of the carbon each visit produces, worked out from how much data the page sends and whether the hosting is green, rated from A+ (lowest) to F by Website Carbon. B or better passes.
The delivery chain
- Third-party content. Most pages load fonts, scripts, maps or video from other companies' servers. The audit checks each of those servers against the same directory, and passes only when every one is green, or when the page loads nothing from elsewhere.
The two published declarations
- A carbon.txt file. carbon.txt is a short text file at a fixed address on the site, readable by software, that says where the evidence for its environmental claims is published. The audit checks that the file exists and follows the published format, version 0.5; a file in the wrong format fails.
- A sustainability statement. A page about the environmental impact of the organisation's own operations (hosting, energy, travel, buying, etc) and what it does to reduce it. Each candidate page is read and scored broad, narrow or none. A page that campaigns on the environment, or mentions it in passing, scores none.
This site publishes both a carbon.txt and a sustainability statement, which seemed the least a page recommending them could do.
Why a green badge alone proves little
Green hosting cleans up the electricity a page runs on. It does nothing about how much data the page sends, and the data is most of what a carbon estimate measures. One site audited this year, a digital agency serving social enterprises, scored top marks for hosting and bottom marks for carbon, because its home page was mostly video. Clean hosting meant the heavy page was running somewhere good.
A green host also says nothing about the fonts, scripts and video loaded from elsewhere, which is why the delivery chain is checked separately. How the calculators treat green hosting, and why the result runs high for a UK site, is on which website carbon calculator to trust.
The two badges
| Badge | Earned when |
|---|---|
| Green Hosting Verified, based on the Green Web Foundation's criteria | The host is in the Green Web Foundation directory |
| Website Carbon Badge, based on Website Carbon's criteria | The page rates A or A+ |
Both are self-assessments made by the audit against criteria the named organisation publishes. Neither organisation has inspected the site, so a badge is a statement of what the audit found and carries no certification.
What you get out of it
Each finding in plain English, sorted into what needs attention, what could improve and what already works, with who acts on it and where: the hosting provider for green hosting, a developer for page weight and third-party content, whoever edits the site for carbon.txt and the statement. Badges not yet earned come with what it would take to earn them.
The effort involved
| Stage | Effort |
|---|---|
| Automated scan of all five checks | Minutes |
| Plain-English report | Produced with the scan |
| Acting on the findings | Depends on the findings, quoted afterwards |
Asking the host about renewable energy and publishing a carbon.txt are quick. A sustainability statement is about half a day, drafted for you to confirm. Cutting page weight and replacing third-party services depend on what is making the page heavy, which the report identifies.
The same audit also tests accessibility, set out on what a website accessibility audit should cover.
The free 90-point audit scan on the website planner page runs all five of these checks. It will tell you how green the site is, and which fixes are worth paying for.
More answers
- Which website carbon calculator should you trust?
- How does a small organisation work out its carbon footprint without buying software?
- What does scope 3 actually require a small organisation to measure?
- What does a net zero roadmap cost when nobody in-house does sustainability?
- Can AI build a custom tool cheaply enough for a small organisation to afford?
- How do you publish a designed document as an accessible PDF and web page?
- How do you collect carbon data from households or members over years, not once?
- What should a website accessibility audit cover, and what does it cost?
- How do you keep a carbon reduction programme going after the first workshop?
- What is my organisation's carbon footprint?
- What should a small organisation ask for when it commissions a website?
- How do you write a web page or LinkedIn post that ChatGPT will quote?
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