What is a cookie?

A cookie is a piece of information placed on your hard drive by the server you visit.
It contains several data:

  • - the server name who filed;
  • - a form of unique identification;
  • - optionally an expiration date ...

This information is sometimes stored on your computer in a simple text file which a server accesses to read and record information.


What are cookies?

Cookies have different functions. They can allow the person who has filed to recognize a surfer, a visit to another, thanks to a unique identifier.
Some cookies can also be used to store the contents of a shopping cart, others to save the language settings of a site, and others to make targeted advertising.


Who can set cookies and access?

A website can only read and write cookies that belong to it.
But we must be aware that internet page often contains information from various sites, including through banner ads.
Therefore cookies may be filed and reviewed by sites other than the one you directly ...
For example, if you browse an information site, it is possible that other websites such as advertising agencies retrieve information about your browsing. For this it is enough that the advertising deposited a cookie on the information site you visit.

How do these advertising cookies?

Advertising cookies record information about the navigation of users, and can deduce their interests or their journey on the website. They then allow companies to customize the advertising that the user will appear depending on the actions performed on the visited site, but also on other sites using the same advertising.
The buttons sharing social networks ("Like" Facebook, "+1" Google, etc.) will allow you to follow in the same way and offer targeted advertising.

How work social buttons as the button "Like" Facebook, Twitter or "+1" Google?

When you visit a web page on which there is one of these buttons, the social network can associate this visualization to your profile. And even if you do not click on the button and if you are not connected on this network! The social network can adapt its advertising compared to sites you have visited and offer "groups" tailored to the interests deducted from your internet browsing. It can also offer you to become a fan of the web page that you visit most.

What does the law in relation to cookies?

The regulation provides that the websites must obtain your consent before filing these cookies, tell you what they are for and how you can prevent it. In practice, a message appears when you connect to the site for the first time to tell you how to accept or decline cookies instead.

How to block cookies?

You'll find advice to install tools that allow you to block certain cookies on the website of the CNIL. For professionals, the CNIL offers fact sheets so they can meet their legal obligations.

How is it possible to know what are the cookies placed on my navigation?

The experts of the CNIL have developed a tool that you can install in a few clicks called CookieViz. It allows you to visualize in real time the extent of cookies and the impressive number of actors involved to analyze your browsing.
All this information on the official website of the CNIL at the following address: