Fingerprinting, a frightening new tool of targeted advertising 


Once the flagship technology of targeted advertising, third-party cookies are disappearing. 
The targeted advertising industry is now turning to more sophisticated techniques, most notably fingerprinting.


  • Metadata, a new fuel for targeted advertising

“Fingerprinting” is a technique used to uniquely identify a user on a website or mobile app, using the technical characteristics of the user’s browser and/or terminal.

The principle is simple: when downloading a web page, the server hosting it can receive a large amount of metadata regarding the terminal making the request. An algorithm can then identify the terminal’s operating system, but also the browser used, its version or the screen resolution. If enough characteristics are provided to it, the various users may be distinguished from each other by elimination.

Fingerprinting therefore makes it possible to follow the browsing of a single user, and to draw up a “consumer profile” from its centers of interest.


  • A practice subject to consent yet invisible

Legally, fingerprinting is assimilated to a “tracer”. When this technique is used for non-essential purposes such as advertising, we must be informed of its existence and consent in order for it to be legal.

Unfortunately, fingerprinting is invisible and painless from the user’s point of view. If the editor of the visited page chooses not to say anything, there is no way to know if our digital fingerprint is taken.


  • Still an intermittent and preventable tracking technique

By its nature, fingerprinting is fortunately limited in time. Identification metadata actually tends to change, thanks to browser updates, add-on modifications, usage of new terminals. Therefore, fingerprinting does not allow long-term targeting.

In addition, there are ways to prevent this practice from tracking a user. Some browser add-ons, such as “CyDec Security Anti-Fp”, can indeed randomly modify the settings transmitted by your browser.


The confrontation between anonymity and web tracking is thus very much ongoing. In this ever-changing context, monitoring and adaptation are key.

A propos de Martin Deloy