What is the _clck cookie?
_clck is a first-party HTTP cookie set by the Microsoft Clarity script when it is embedded on a website. Clarity is a free behavioral analytics service from Microsoft that provides heatmaps, session recordings, and interaction reports.
The cookie is created as soon as the Clarity script loads and runs on a page, regardless of whether the visitor actively interacts with the site or simply views it.
What data it stores
The _clck cookie stores a randomly generated unique identifier (Clarity User ID) that stays consistent across multiple sessions and visits from the same browser. The value is an alphanumeric string with no directly identifiable information, but it functions as a persistent device/browser identifier.
Data collected through this identifier (pages viewed, mouse movement, clicks, scrolling) is sent to Microsoft Clarity's servers for processing and displayed in the site owner's reporting dashboard.
What it is used for
For Microsoft, the cookie allows linking multiple sessions to the same visitor, so behavioral reports (heatmaps, session replay) correctly reflect a single user's journey over time rather than isolated single visits.
For the website owner, this results in more accurate insights into how visitors navigate the site, where they struggle, or where they drop off — information used to optimize UX and conversions.
Does it require consent?
In CookieFix's classification, _clck falls under the statistics/analytics category. Since it is used solely for behavioral measurement, it is not strictly necessary for the website to function.
- Under GDPR and the ePrivacy Directive (transposed in Romania via Law 506/2004), this cookie requires the visitor's prior, explicit consent before being placed.
- The site owner must disclose it in the cookie policy, including its category, provider (Microsoft), and actual duration.
- The Clarity script should only load after consent for the statistics category has been obtained, not by default on page load.
How to block or delete _clck
A visitor can manually delete or block the cookie from browser settings (Chrome, Firefox, Edge, Safari – cookie and site data management sections), or use tracking-blocking browser extensions.
From the site owner's side, the correct approach is to have the Microsoft Clarity script blocked automatically until the visitor gives consent for the statistics category. A consent management platform like CookieFix can handle this automatically, preventing the Clarity script from loading before consent and activating it only after acceptance.
Frequently asked questions
It does not directly contain sensitive data, but its value acts as a persistent browser identifier, which is why it is treated as personal data under GDPR.
The typical duration is about 1 year, though this can vary depending on Clarity's configuration or browser policies.
Yes, since it's a statistics/analytics cookie, it requires the visitor's prior consent under Romanian and EU privacy law.
The Clarity script should not set the cookie, and the site won't be able to link that visitor's sessions across visits, but the site's core functionality is not affected.