Sustainability statement

Like any digital product, this website has an environmental impact, which we present on this page using standardized metrics.

We use the EcoIndex framework provided by the GreenIT.fr, to assess the environmental performance of this website. This performance is quantified using two types of indicators:

• The website’s eco-design level.This indicator assesses the implementation of best practices to reduce a web page’s environmental impact. The level achieved is represented by a relative rating from A to G (A being the highest rating) combined with an absolute score from 0 to 100 (100 being the highest score).
• Water consumption and GHG emissions associated with page loading. This indicator quantifies freshwater consumption ( cls) and GHG emissions ( gCO2e) associated with loading a web page.

For summary purposes, four types of data are presented:

• Eco-design level for the 5 most-visited pages on the website
• Eco-design level for 5 typical user journeys on the website
• Water consumption (in liters) and GHG emissions (kilograms of CO2e) associated with loading a web page for 1 user, normalized to 1,000 users.
• Water consumption (in liters) and GHG emissions (kilograms of CO2e) associated with completing a user journey for 1 user, normalized to 1,000 users.

The analysis shown was conducted on August 18, 2026, and is subject to change: the quantification of environmental impacts presented below is a snapshot taken at a specific point in time.

Page 1: Our Scientific Projects

• Water consumption per 1,000 users: 20.1 liters, or 2 packs of mineral water.
• GHG emissions per 1,000 users: 1.34 kilograms of CO2e, equivalent to a 6-kilometer drive in a gasoline-powered car.

Link to the EcoIndex results page

Page 2: Cities

• Water consumption per 1,000 users: 20.7 liters, or 2 packs of mineral water.
• GHG emissions per 1,000 users: 1.38 kilograms of CO2e, equivalent to a 6-kilometer trip in a gasoline-powered car.

Link to the EcoIndex results page

Page 3: Team

• Water consumption per 1,000 users: 25.2 liters, or 3 packs of mineral water.
• GHG emissions per 1,000 users: 1.68 kilograms of CO2e, equivalent to an 8-kilometer trip in a gasoline-powered car.

Link to the EcoIndex results page

Page 4: CoolSleep Project

• Water consumption per 1,000 users: 20.1 liters, or 2 packs of mineral water.
• GHG emissions per 1,000 users: 1.34 kilograms of CO2e, equivalent to a 6-kilometer trip in a gasoline-powered car.

Link to the EcoIndex results page

Page 5: Our Publications

• Water consumption per 1,000 users: 19.2 liters, or 2 packs of mineral water.
• GHG emissions per 1,000 users: 1.28 kilograms of CO2e, equivalent to a 6-kilometer drive in a gasoline-powered car.

Link to the EcoIndex results page

Path 1: Learn about CITÉS’ scientific projects

• Objective of this path: Find information about ongoing scientific projects.
• Target activity: Loading the homepage + Loading the “Our Scientific Projects” page

• Water consumption per 1,000 users: 40.8 liters, or 4 packs of bottled water.
• GHG emissions per 1,000 users: 2.72 kilograms of CO2e, equivalent to a 12-kilometer drive in a gasoline-powered car.

Scenario 2: View CITÉS Team Members

• Scenario Objective: Be able to contact CITÉS team members.
• Target path: Loading the home page + Loading the Team page

• Water consumption per 1,000 users: 45.9 liters, or 5 packs of bottled water.
• GHG emissions per 1,000 users: 3.06 kilograms of CO2e, equivalent to a 14-kilometer trip in a gasoline-powered car.

Module 3: View CITÉS Publications

• Module objective: Access the CITÉS team’s publications.
• Target module: Loading the home page + Loading the “Our Publications” page

• Water consumption per 1,000 users: 39.9 liters, or 4 packs of bottled water.
• GHG emissions per 1,000 users: 2.66 kilograms of CO2e, equivalent to a 12-kilometer trip in a gasoline-powered car.

Eco-design is based on a methodology and a set of best practices designed to reduce this website’s environmental impact. In practical terms, this involves minimizing the technical resources required to display a page or execute a feature, while meeting the user’s needs as closely as possible.

Are you a digital professional looking to reduce the environmental impact of your websites? Here are some best practices to implement:

Best practices for usability and design

• Limit the number of features from the design phase onward
• Remove unused features
• Limit the number of carousels
• Choose lighter font weights
• Favor simple, clean designs
• Adopt a “mobile-first” approach whenever possible
• Prefer pagination over infinite scrolling
• Avoid automatic playback and loading of videos and audio
• Optimize user flows
• …

Some Best Practices for Content Management

• Use images instead of videos
• Limit the number of images on each page
• Optimize image size for the target format
• Compress images using a tool such as TinyPNG
• Compress PDFs using a tool such as iLovePDF
• Limit the use of animated GIFs
• Use glyphs instead of images
• …

Some best practices for development

• Use asynchronous processing whenever possible
• Use only the essential parts of JS and CSS libraries
• Cache frequently used computed data
• Limit the number of HTTP API calls
• Reduce the volume of stored data to the bare minimum
• Use the latest version of the language
• Provide a text alternative for multimedia content
• Split up CSS files
• Do not modify the DOM while traversing it
• Use lazy loading (lazyload)
• Validate pages with the W3C
• Add Expires or Cache-Control headers
• Compress text files: CSS, JS, HTML, and SVG
• Set up an efficient sitemap
• …

Some Best Practices for Web Hosting

• Choose an Eco-Friendly Hosting Provider
• Install Only the Minimum Required on the Server
• Use managed services
• Optimize server energy efficiency
• Reduce server logs to the bare minimum
• Apache Vhost: Disable AllowOverride
• Use virtualized servers
• Use an asynchronous server
• Store data in the cloud
• …

To prepare your environmental declaration:

Access the documentation

To view the complete list of best practices for eco-friendly web design:

Go to the GreenIt website

Access the GreenIt repository (GitHub)

To learn more about EcoIndex:

Learn more about the EcoIndex framework

Visit the EcoIndex website

*Average environmental impact of the 5 most-visited pages on this website.