At Contribution on the subject of cookie consent it has already been pointed out that the website statistics tool Matomo can also be operated without the use of cookies. This raises the question: Why are cookies used in Matomo at all and what are the consequences of deactivating them?
Why cookies?
Cookies are used in Matomo for several purposes. The first purpose is the Identification of returning visitors. If a Matomo cookie from a previous visit is found on the client computer when a website tracked with Matomo is accessed, a comparison can be made with the existing inventory data. How often has the page already been accessed from this computer, when was the last time? How long did the individual visits last and - very important for web analysis - did visits to certain pages such as advertised landing pages or product pages only lead to the achievement of goals defined in Matomo such as orders, contact enquiries or similar on later visits?
Recognition is pseudonymous: a string of characters generated from random values stored in the cookie is sufficient as an ID for matching.
The second purpose is, somewhat paradoxically at first glance, the Storage of the refusal of Matomo tracking by using the opt-out function on the part of the user.
Finally, another purpose is the storage of the release for tracking, provided Matomo is implemented as an opt-in solution with an explicit request for consent from the user.
Details on the cookies set by Matomo can be found at [1].
What happens without cookies?
If cookies are not available to recognise users over several visits, Matomo instead creates a profile ("fingerprint") based on various properties of the accessing device (device type, browser version, screen resolution, etc.) and stores it on the server. However, identification based on the fingerprint is less accurate than when cookies are used.
Consequently, the deactivation of cookies is at the expense of the measurement accuracy of those parameters that are based on recognition. The "unique visitors" value tends to become less accurate, while the pure number of visits, for example, is not affected. The display of visitor profiles in the visitor log is also affected.
As a further consequence, it is no longer possible to assign target achievements/conversions to the original entry point over several visits. If a user comes to the website with a specific search term or, for example, via a specific link from an advertising campaign, but only reaches a goal on a later visit, this goal achievement is assigned to the entry of this visit, for example as a "direct call", and not to the entry via the advertising campaign.[2]
On the other hand, this allocation has limits even with cookies activated and only works if all visits are made with the same browser and no cookies are deleted or expire in the meantime.
Get rid of cookies, this is how
If you only want to track one or a few sites and deactivate cookies for all of them, it's very simple: Under "Settings/privacy/anonymise data", tick the box "Force tracking without cookies", then the script code provided by the Matomo server is automatically adjusted accordingly, which affects all measured sites.[3]
If you want to use cookie-free and cookie-supported tracking in parallel within a Matomo installation, add the instruction "_paq.push(['disableCookies']);" before "_paq.push(['trackPageView']);" to the tracking code for the cookie-free sites.
The finished tracking code, including the corresponding addition, can be conveniently generated automatically under "Settings/Websites/Tracking code". To do this, click on "Show" under "Advanced", then tick the box for "Disable all tracking cookies", copy the code displayed in the text field and paste it into the target website.
[1] https://matomo.org/faq/general/faq_146/
[2] https://matomo.org/faq/general/faq_156/
[3] https://matomo.org/faq/general/faq_157/
Continuing:
https://matomo.org/faq/new-to-piwik/how-do-i-use-matomo-analytics-without-consent-or-cookie-banner/
https://matomo.org/blog/2018/04/how-to-not-process-any-personal-data-with-matomo-and-what-it-means-for-you/
