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What is a web page made of?

Authors and date
  • Submitted on: April 13th 2021
  • Laurent Devernay ; Referent Trainers Occitania ;


The awareness of the environmental impact of digital technology invites us to put our uses in context. In particular, it is important to understand the problems related to web pages. The starting point is simple: web pages are increasingly large and are now several MB in size (2 MB on average, compared to 1.5 MB in 2017 and 700 KB in 2012).

  • Evolution of the weight of web pages (HTTP Archive)1

Even if our Internet connections are getting faster, our web browsing is getting slower, and the impact on the amount of data we consume keeps rising (keeping in mind that not everyone is lucky enough to have an unlimited data package!2). As you will see in this MOOC, the environmental impact increases with the size of the pages.

What is a web page made of?

In the beginning, web pages had only text, presented as HTML3(HyperText Markup Language), a content structuring language. Then came CSS4(Cascading Style Sheets): style sheets to define the appearance of content. Then, various languages appeared to add some dynamism as JS (JavaScript)5 and its weight which has become very important6 and even business logic (filling out your tax return online, for example). The content found on websites has also been enriched with images, music, videos, files, etc. The overall idea is to offer more content, in more varied forms, and to take advantage of the ever-increasing possibilities offered by the Web.

In addition to all this, the business model has changed. To keep the Web free, trackers and advertisements have appeared.

Online advertising

A few years ago, online advertising already represented 39% of the weight of web pages:

  • study on privacy and performance via Mozilla Firefox7
  • study on the environmental impact of online advertising 8

On average, nowadays a person sees between 4000 and 10000 ads per day9. However, this economic model is starting to show its limits10, especially because it remains difficult to estimate the revenues generated. Many newspapers have taken this path to compensate for the announced decline of the paper press. Today, more and more newspapers are going back to more traditional subscription models11, which provide incentives to produce quality content.


Trackers are pieces of code designed to collect information about Internet users and in particular about their browsing (pages visited, searches performed, etc.). Google, in particular, provides many tools for this data collection, starting with Google Analytics. Its primary cause for adoption is to allow website owners to know more about the uses of their visitors in order to optimize websites. But it is mainly a way for the web giant to accumulate even more information. However, Google Analytics has a significant environmental impact and these trackers are now present on almost all websites:

  • estimation of the environmental impact of Google Analytics12
  • distribution of trackers on the web (WhoTracks.me13)
  • 2020 state of play on the collection of personal data on the web14

Google Analytics has even been deemed illegal in some european countries15.

What to do?

As we have seen, newspapers are paving the way to a lighter web by looking for other incomes than online advertising. More generally, those who create sites must keep in mind as a priority sobriety (less media, more relevant and updated content) but also the optimization of media (images, videos) and tools used.

As a user, it is advisable to look at the side of tools allowing to block ads (uBlock16) and trackers (Blacklight17, Ghostery18).


  1. [07/06/2021] 

  2. Chris Ashton. I Used The Web For A Day On A 50 MB Budget [online]. Smashing magazine, 07/2019. Available at [07/06/2021] 

  3. Discover HTML on [07/06/2021] 

  4. Discover CSS on [07/06/2021] 

  5. Discover JS on [07/06/2021] 

  6. Tim Kadlec. The Cost of Javascript Frameworks [online], 04/ 2020. Available at [07/06/2021] 

  7. Advertising accounts for 39% of web page weight. Tracking Protection in Firefox For Privacy and Performance [07/06/2021] 

  8. M. Pärssinen, M. Kotila, R. Cuevas, A. Phansalkar, J. Manner. Environmental impact assessment of online advertising [online]. Environmental Impact Assessment Review, Vol. 73, 2018, Pages 177-200. Available from [07/06/2021] 

  9. How Many Ads Do You See Each Day? Available at [07/06/2021] 

  10. Jesse Frederik, Maurits Martijn. The new dot com bubble is here- it's called online advertising [online]. The Correspondent, 11/2019. Available at [07/06/2021] 

  11. Gilad Edelman. Can Killing Cookies Save Journalism? [online]. Wired, 05/2020. Available at [07/06/2021] 

  12. Gerry McGovern. Calculating the pollution cost of website analytics (Part 1). 08/2020. Available at [07/06/2021] 

  13. [07/06/2021] 

  14. Web Almanac 2020 - Privacy [07/06/2021] 

  15. Google Analytics declared illegal in some european countries - FR [20/01/2022] 

  16. [07/06/2021] 

  17. [07/06/2021] 

  18. [07/06/2021]