What are cookies?

Cookies are small text files placed by your browser on your device when you visit a website to store certain information. Using the stored information, a website can recognize that you have previously accessed and visited it using the browser on your end device.

How do we use cookies?

CERN uses cookies to arrange and display the website optimally in accordance with your preferences (such as login, language, font size and other display preferences) so that you do not have to keep re-entering preferences each time you visit the website.

Which cookies do we use?

Necessary Cookies

These cookies are necessary for the functioning of the website.




Used for

cerndrupal_prod_https End of session Used for load balancing to distribute incoming traffic across a backend servers.


1 year

Used to record which cookies the web user has consented to.

SimpleSAMLAuthToken, SimpleSAMLSessionID 8 hours validity tokens or until logged out Used, only when a web user logs in with a username and password, to distinguish authenticated sessions.
SSESS... End of session Used, only when a web user logs in with a username and password, to keep track of the current authenticated session.

Matomo Analytics

CERN uses Matomo Analytics (formerly PIWIK) to analyse traffic to the website and help improve website performance. Embedded videos from the CERN Document Server (CDS) also use Matomo Analytics to track viewing statistics.
Matomo Analytics data is stored at CERN.

If you disable Matomo Analytics cookies, you will not be able to view embedded CERN videos from the CERN Document Server (CDS).



Used for

_pk_id... 13 months Used to distinguish web users


6 months

Used to log how a web user got to the website e.g. via a search engine, newsletter, direct link etc.

_pk_ses... 30 minutes Used to keep track of the current session
session End of session Used by, only when there is an embedded CERN Document Server (CDS) video on a webpage, to track statistics and provide a better user experience e.g. replaying a video from where the user previously stopped watching.

For more details, see this Matomo webpage.

Google Analytics

This CERN website uses Google Analytics to see how many visitors have come to the website, from where and for what duration of time, to understand how CERN’s web content is performing and to gain insights to improve future content. Please note: this website does not use the advertising or marketing features of Google Analytics.

If you disable Google Analytics cookies, you will not be able to view embedded CERN videos from third-party services e.g. YouTube and Vimeo.



Used for

_gat 10 minutes Used to throttle request rate


2 years

Used to distinguish users

_gid 1 day Used to distinguish users

How to control cookies

You can control and/or delete cookies as you wish – for details, see You can delete all cookies that are already on your computer and you can set most browsers to prevent them from being placed. If you do this, however, you may have to manually adjust some preferences every time you visit a site and some services and functionalities may not work.

Further information

Read our full data privacy protection policy