What is the `ANONCHK` Cookie?

Set by Microsoft (Microsoft Corporation). Expires after 10 minutes.

Purpose

Stores a session ID used to verify ad-click quality and for page analytics on Microsoft properties such as Bing and Clarity.

Short-lived but advertising-related, so it still requires consent. Usually set alongside MUID.

Marketing cookies are used to track visitors across websites to display relevant advertisements. Consent is required under GDPR.

Under GDPR and the ePrivacy Directive, the ANONCHK cookie requires explicit user consent before it can be set. This means:

The cookie must not be set when a user first visits your site — not even for a fraction of a second
A consent banner must be displayed, and the user must actively accept analytics/marketing cookies
If the user rejects or ignores the banner, this cookie must remain blocked
The cookie must be listed in your cookie policy with its name, purpose, and retention period
Users must be able to withdraw consent at any time, which must also remove or invalidate this cookie

Block it by default — configure your Consent Management Platform (CMP) or tag manager to prevent Microsoft from loading until the user accepts marketing cookies.
Include it in your consent categories — map it to the "Marketing / Advertising" category in your CMP configuration.
List it in your cookie policy — document the cookie name, purpose, provider (Microsoft Corporation), and expiry (10 minutes).
Sign a DPA — ensure you have a Data Processing Agreement with Microsoft Corporation covering their use of data collected via this cookie.
Verify it works — in an incognito browser, reject cookies and confirm ANONCHK is not set.

Cookie	Category	Duration
MUID	Marketing / Advertising	13 months
MR	Marketing / Advertising	7 days

Scan your website to see every cookie it sets, whether they're blocked before consent, and get a full GDPR compliance report.