What is the ANONCHK cookie?
ANONCHK is a technical cookie associated with Microsoft Clarity, Microsoft's free user-behavior analytics service (heatmaps, session recordings, click tracking). It is set by the Clarity script when it loads on a website.
It typically appears on the visitor's first interaction with the page, alongside other Clarity cookies (such as those storing a session ID). The associated domain is in the form clarity.ms.
What data it stores
ANONCHK generally stores a status flag indicating whether the transfer of identification data collected by Clarity to Microsoft's servers is allowed for the current session. Its exact value format isn't publicly documented and may vary by script version.
It is an HTTP cookie with a Session lifespan – it disappears automatically when the browser is closed. Associated data is sent to Microsoft's Clarity infrastructure, not to unrelated third parties.
What it is used for
The cookie's purpose is strictly technical: it helps the Clarity script decide whether it can continue collecting and transmitting behavioral data (mouse movements, scrolling, clicks, session recordings) for that session.
For site owners, this data translates into usability reports: where visitors get stuck, which page areas they ignore, and where interface errors occur – information used to improve the site, not for direct advertising.
Does it require consent?
CookieFix classifies ANONCHK under the statistics category. Because Microsoft Clarity collects behavioral data (and, depending on configuration, may combine it with other Microsoft services), this cookie does not qualify as "strictly necessary" under ePrivacy/Romanian Law 506/2004 and requires the visitor's explicit consent before being set.
- The Clarity script should be blocked until the "statistics" category is accepted in the banner.
- The cookie and its purpose must be disclosed in the site's cookie policy.
- Site owners should review the data processing agreement (DPA) Microsoft offers for Clarity.
How to block or delete ANONCHK
Visitors can delete or block ANONCHK from their browser settings (Chrome, Firefox, Edge, and Safari all allow deleting cookies per domain, including clarity.ms), or decline the "statistics" category in the site's consent banner, if one is properly configured.
For site owners, the safest approach is to automatically block the Clarity script before consent is given. A CMP such as CookieFix can prevent the Clarity script from loading (and thus stop the ANONCHK cookie from being set) until the visitor explicitly accepts the statistics category, avoiding premature setting of analytics cookies.
Frequently asked questions
It's a session cookie set by Microsoft Clarity, used to check whether the user's identification data can be sent to Microsoft's servers during the current visit.
It's not an advertising cookie, but a behavioral analytics one (heatmaps, session recording). Still, since it collects data about visitor behavior, it isn't considered "strictly necessary."
Yes, as it falls under the statistics category, it requires prior consent under GDPR and the ePrivacy Directive (transposed in Romania via Law 506/2004) before being set.
You can delete cookies for the clarity.ms domain in your browser's privacy settings, or decline the statistics category in the site's cookie banner.