# Sustainability Audit of University Websites in Poland:
## 3 Materials and Methods
### Measurement Tools and Quality Indicators  
The study spans 5-8 May 2025 and covers only the homepages of university websites. The author measured 15 sustainability and technical quality metrics for each website, including such items as carbon emissions, asset size, load times, and selected SEO indicators. A total of 945 unique manual measurements were performed and used in further analyses (Supplementary Materials). The study employs selected measurement tools. All tools were used under identical, standardised technical and networking conditions. Research design validity was ensured by taking measurements during low-traffic hours, specifically between 10:00 a.m. and 3:00 p.m. local time (CEST, UTC + 2). The websites were tested without preloading (i.e., with no cache) and with browser extensions disabled. The tests were conducted with Mozilla Firefox v. 138.0.1 (released on 1 May 2025) and Lighthouse v. 12.0.0 (released on 22 April 2024). The measured values were tabulated in a standardised manner to facilitate statistical and comparative analysis. The author employed dedicated website sustainability auditing tools: (1) Ecograder (Mightbybytes, Chicago, IL, USA), (2) Website Carbon Calculator (Wholegrain Digital, Scamper Ltd., Exchange at Somerset House, South Wing, Strand, London, UK), (3) DigitalBeacon (Aline, Cambridge, UK), and (4) Kastor Green (Specinov, France). This approach conforms to the cross-validation principle, where quality measurements are made using at least two tools. Additionally, the author conducted an AI audit with an original AI Custom GPT agent preconfigured in the ChatGPT ecosystem, Green Web Audit Assistant (ChatGPT Plus, OpenAI) [47], followed by mobile and desktop SEO audits. The measured values (Table 2) were saved to a database. The audit yielded values for selected quality indicators, enabling a comprehensive assessment of the websites' environmental impact. The indicators were selected following a review of available tools and practices for environmental optimisation of websites. The specific sources include documentation for EcoGrader, Website Carbon Calculator, and Digital Beacon, which implement principles in line with the current trends in sustainable digital development [38; 45]. Qualitative indicators include page size (MB), the number of HTTP requests, the use of multimedia files, and green hosting [18; 37]. Moreover, some metrics were complemented with additional technical analyses based on the literature and their comparative potential [20]. Ecograder measures the Ecograder Score, ranging from 0 to 100. It covers factors such as green hosting, page loading time, the number and size of page components (page assets), and energy-efficient design. This assessment is complemented by CO\({}_{2}\) emissions per page load in the browser window, measured in grams. The lower its value, the smaller the environmental burden of the website. Another critical parameter is page assets. It is the total size of transferred data in megabytes (MB). Additionally, Ecograder rates each website. It assigns a digital carbon rating (DCR), a letter mark ranging from A (the best) to F (the worst). It reflects the website's general emissions intensity. The Website Carbon Calculator employs a similar classification with letters. It assigns a carbon rating and calculates CO\({}_{2}\) emissions in grams per page load. Digital Beacon calculates the carbon footprint, expressed as letters, and estimates emissions caused by the first visit to the website (first visit CO\({}_{2}\)) with browser cache disabled. It also measures the page size on the first load to cover asset impact before the browser even saves the data locally. In addition to CO\({}_{2}\) emissions per page load, Kastor Green estimates (1) the Global Score, an integrated sustainability and user quality indicator (0-100) and (2) the Ecodesign Score, focused on sustainable design quality. Kastor Green's evaluation includes aspects such as the website's structure, typography, contrast, and accessibility.