Somebody will eventually ask you if you’ve ever done a website carbon audit!
A procurement questionnaire, a tender, a client with reporting obligations of their own.
The wrong answer is a number you got from a free tool three months ago and cannot explain. The right answer is a figure, a method, a date and a set of conditions.
A website carbon audit is not complicated. It is mostly the discipline of writing down what you did, which is the part that turns a number into evidence.
Gloucestershire Website Carbon Audit: What to Look For
Not emissions. An estimate derived from them.
Carbon calculators take the data your page transfers and apply modelled assumptions about the energy required to move and process it, the carbon intensity of the electricity involved, and whether the hosting is renewable-powered.
Published models such as the Sustainable Web Design methodology give figures for the emissions associated with an average page view, and those figures have been revised as the underlying research has developed. Any number you quote should name its source and its version, because the same page assessed under two methodologies produces two answers and neither is wrong.
The method, step by step
- Choose your pages. Your five to ten most-visited, from analytics rather than intuition. The homepage is rarely the whole story.
- Record the conditions. Which device, which connection, first or repeat visit, and the date. Without these, nothing you measure later is comparable.
- Measure page weight and requests. Browser network panel, cache disabled, sorted by size.
- Measure Core Web Vitals. Under the same conditions.
- Run a carbon estimate. One tool, applied consistently. Note which and what version.
- Check your hosting. Whether your provider claims renewable power, and what that claim actually covers. The Green Web Foundation’s hosting check tells you whether a host appears in its directory, which is a starting point rather than a full verification.
- Multiply by traffic. A heavy page with fifty views a month matters less than a moderate page with fifty thousand.
Write all of it down in one place. That document is your baseline and the thing you will be glad of in six months.
What the results usually show
Three patterns turn up on almost every site that has never been reviewed.
Images dominate page weight, and most are served larger than they display, in dated formats, loaded eagerly.
Third-party scripts account for more than anyone expects, and several belong to tools nobody has opened in a year.
The homepage is rarely the worst page. Product pages, galleries and anything built by a marketing campaign usually are.
Fixing what you find
In order of return: images, then unaccounted third-party scripts, then fonts, then JavaScript.
Re-measure after each change under the same conditions, so you can attribute the improvement rather than guessing at it.
Where performance and environmental impact both apply, treat them as the same lever: reducing unnecessary data transfer and processing supports a faster experience while lowering estimated digital carbon, though environmental figures remain modelled rather than directly measured.
Why local benchmarks do not exist
You may want to know how your site compares to other Gloucestershire businesses. No credible dataset for that exists, and anyone offering one should be asked how they gathered it.
What does exist is national and global data on page weight across the web, which is a legitimate comparison. Your own trend over time is more useful still, because it controls for everything specific to your sector and audience.
Reporting it safely
Environmental claims must be accurate and substantiated. The Competition and Markets Authority’s Green Claims Code sets out the standard.
State the figure, the tool, the conditions, the date and the scope. Say plainly that the figure is a modelled estimate covering website delivery rather than your organisation’s digital footprint.
That framing is both accurate and more credible to anyone assessing it, because it demonstrates you understand what you measured.
Our website sustainability audits follow this method and document it, which is what makes the output usable in a tender.