What is the ANONCHK cookie?
The ANONCHK cookie is a third-party operational flag set by Microsoft Clarity to indicate whether a user's MUID is synced with Microsoft's advertising cookies.
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About ANONCHK
| Vendor | Microsoft |
|---|---|
| Cookie Domain | clarity.ms,microsoft.com,msn.com,office.com |
| Category Category The functional category of the technology, such as Web Analytics or Social Media. Learn more | Heatmap & Recording |
| Consent Category Consent Category The consent category this cookie most commonly falls under across sites we scan, normalized into four standard categories. Learn more | Targeting & Advertising |
| Prevalence | Very Common |
| Popularity Popularity Popularity is calculated from our dataset of 4.5B+ cookies analyzed across hundreds of millions of web pages. Learn more | Found on 11.3% of scanned pages |
| Expiration Type | Timestamp |
| Party Type Party Type Whether the cookie is first-party or third-party. Learn more | 3rd-Party |
| Risk Level Risk Level Rates how sensitive the data stored by this cookie is (High, Medium, or Low) based on data classification and distribution. Learn more | Low |
| Vendor Privacy Policy | https://privacy.microsoft.com/en-us/privacystatement |
| Vendor Website | https://www.microsoft.com |
What is the purpose of ANONCHK?
The ANONCHK cookie is a third-party cookie set by Microsoft Clarity, a behavioral analytics and session recording tool. Its primary function is to indicate whether the user's MUID (a unique browser identifier) has been transferred to the ANID cookie, which is used by Microsoft for advertising purposes. For Microsoft Clarity implementations, this flag is consistently set to '0' because Clarity does not utilize the ANID cookie for advertising.
Although the cookie itself only stores a single-character boolean flag, it plays a role in Microsoft's broader analytics and advertising network infrastructure by verifying session details and preventing fraudulent ad clicks on the Bing search engine. It does not store personal identifiers directly, but rather dictates the syncing behavior of other identification cookies across Microsoft domains.
What are the Privacy Risks of ANONCHK?
Risk Level: Low
The ANONCHK cookie poses a low privacy risk as it solely stores a single-character boolean flag (typically '0') rather than a unique online identifier or personally identifiable information. Its specific purpose is to signal whether the user's MUID has been transferred to Microsoft's ANID advertising cookie. While it is associated with Microsoft Clarity (a session recording tool that operates across domains), the ANONCHK cookie itself does not enable cross-site tracking or profiling, and it carries no unique per-user identifier in its value.
How to Remove ANONCHK from a Website
To remove the ANONCHK cookie, website administrators must disable or remove the Microsoft Clarity tracking script from their website's codebase or tag management system (for example, deleting the Clarity tag from Google Tag Manager or removing the Clarity setup snippet from the page <head>). Because ANONCHK is a core operational cookie set automatically by Microsoft Clarity's third-party infrastructure, it cannot be individually disabled or removed while Microsoft Clarity remains in use. There is no account-level setting that suppresses only this cookie, so the only reliable way for the site operator to stop it from firing is to remove the Microsoft Clarity service entirely.