About
About the criteria
Lowwwimpact's criteria are grounded in the W3C Sustainability Group guidelines, adapted to capture the essential considerations for a sustainably designed and developed website.
Before its broader release, this product was developed internally at Liip to better integrate eco-design practices into our work. As part of this effort, we streamlined the criteria used to evaluate a website, focusing on those that best support continuous improvement. Three scopes have been defined so far, with more scopes and criteria likely to be added in the future.
Rating system
At this time, no official rating system exists for web sustainability based on W3C criteria. Lowwwimpact proposes one with the goal of continuous improvement — providing clients with concise results alongside actionable recommendations, which can also be used for communication purposes, provided the discourse remains free of greenwashing.
The rating system is always relative to the scope selected for a given evaluation. It is important to note that an "A" rating under the "Essential" scope does not equate to the same performance under the full scope — in fact, it would likely correspond to a "D."
The 27 criteria in the "Essential" scope are considered quick wins, meaning they carry more weight in the evaluation than standard criteria. To illustrate: having all Essential criteria satisfied within the full scope accounts for approximately 60% of the total points, while representing only 30% of the criteria — following a principle similar to the Pareto effect.
Ratings are assigned based on the percentage of total obtainable points:
- A › 90.00%
- B › 78.00%
- C › 66.00%
- D › 54.00%
- E › 42.00%
- F › 30.00%
- G › 29.99%
Lowwwimpact may evolve depending on whether the W3C Sustainability Group introduces its own rating system. The point system is also subject to refinement over time. A potential long-term goal is to allow users to create and customize their own criteria and scoring systems, though this is not currently on the roadmap.
Carbon intensity methodology
Lowwwimpact allows you to measure the carbon footprint of a webpage. Rather than developing an entirely new calculator — like Ecograder or Website Carbon — we simply ask you to input your webpage's network usage and combine it with an energy mix. Following the sustainablewebdesign.org estimation model, this makes it possible to provide a CO₂ equivalent estimation.
By default, the carbon intensity used is the world average (approximately 494g/kWh). Since the carbon intensity of electricity varies from country to country, knowing where the majority of your users are located, where your product is hosted, and which energy sources power it can help you obtain more accurate estimations.
For example, if your product is hosted in Switzerland on renewable energy and 80% of your users are based in Switzerland, it makes sense to apply a custom energy mix rather than relying on the world average. In practice, this means that a webpage may have a lower carbon footprint for the same network usage, depending on where the website is hosted and browsed.
We recommend creating a custom carbon intensity value only if you have sufficient and reliable sources to support it.
How to measure the correct page weight?
Using your browser's developer tools
Open the developer tools in your web browser and navigate to the "Network" tab. Before reloading the page, make sure to disable the cache. Once the page has loaded, look for the total "kB transferred" value. You will need to record this value twice: once after the initial page load, and once after scrolling to the bottom of the page.
Using the Lowwwimpact Chrome Extension
To simplify this process, we have built a Chrome extension available for Google Chrome and Brave Browser. Simply run the extension on the webpage you wish to evaluate and retrieve the network usage value directly.
How to define a plausible carbon intensity?
For the time being, we provide a spreadsheet to help you define a plausible carbon intensity value, along with reference data to guide you. We recommend defining a carbon intensity based on a specific country, like targeting users in Switzerland or Germany, for example.
Carbon intensity is split into three segments: Data Centers, Network, and User Devices.
Estimating the impact of the network segment remains particularly challenging, as the route data takes from a data center to a device can vary and is difficult to determine with precision. For this reason, the network segment will always default to the world average (494g/kWh). However, it is possible to refine the values for the data center segment (based on the carbon intensity of the electricity powering it) and the user device segment (based on the carbon intensity of the electricity used by end-user devices).
For example, in Switzerland, one source suggests that the carbon intensity of consumed electricity is around 125g/kWh, while another estimates a lower average of 65g/kWh. We recommend defaulting to the higher value when in doubt, but it is up to you to assess and determine the reliability of the sources you use.
To better understand how the calculation model works in detail, visit sustainablewebdesign.org.
