100 points to know about...
Digital accessibility

If you have consulted the two modules of this platform dedicated to web ecodesign and web accessibility, you have probably noticed some common points between these two approaches.
Generally speaking, these two approaches are perceived as initially generating an additional development cost compared to a classic development. If there is often an initial financial effort, it may prove beneficial later on.
The earlier the actions are thought out, the lower the initial investment will be. If the thinking is done during the design phase, the constraints can be taken into account during the development phase. But if it is necessary to intervene afterwards on a site or an application that has not been designed responsibly, the costs of compliance can be much higher.
On the other hand, since the essence of an eco-designed site is its frugality and simplicity, one can think that by avoiding non-essential pages and superfluous animations, the site will be less costly to produce.

"When working on web accessibility, one finds frequently that some practices result in reducing the size of pages, or the amount of data transferred to the user. Furthermore, an accessible web site is generally simpler and therefore faster to view , not only for users with disabilities."
(French Open Web Group, ACCESSIBILITY IS GOOD FOR THE PLANET)

Simplification of content

Indeed, one of the common points between ecodesign and accessible design is the simplification of contents. The simpler the contents are, the easier they are to understand and to interpret in different ways, so the more accessible they are, the lighter they are in terms of memory. Faster to display, requiring less bandwidth on the servers, so less energy consumed. Limiting the size of text, optimizing the weight of images to be displayed, limiting videos are good practices that serve accessibility and limit the impact in terms of energy consumption.
Limiting your number of fonts and using only system fonts (such as Sans Serif fonts) is both more accessible and eco-friendly (as new fonts don't have to be downloaded).
Also, removing the clutter from your code creates more simplified (ie. accessible and eco-friendly) websites.

SEO

As we have seen before, all the practices presented in this module, aiming at informing at best what is presented on the screen and which facilitates the reading for the various types of handicaps, participates in an optimization of the SEO.
This has a strong impact on the referencing of sites, and the improvement of search results, with the consequence of a strong reduction of useless client-server requests, since we arrive more directly at what we are looking for. These requests are identified as one of the most important items of the web energy consumption.
Properly captioned images, systematically subtitled video content, well-structured web pages with titles, subtitles and paragraphs, necessary for better accessibility, can therefore significantly reduce the carbon footprint of the web.

Personalization

As we have seen with the concept of flexibility of use, when the design adapts to a wide range of individual preferences and abilities, the possibilities of customizing the display of web pages are multiplied.
This approach, necessary for the most universal accessibility possible, also allows users to choose what they want to consult according to their real needs, to display only what they need.
For energy saving reasons, some sites propose for example today to display images only on explicit request of the user, rather than loading and displaying them systematically or loading and starting videos automatically. We therefore limit by default the loading of these elements, and users can decide to do it with full knowledge of the facts and awareness of their impact in terms of energy (with for example display of the weight of the downloaded files and equivalent in terms of energy consumption).