What is the SM cookie?
SM is a cookie set by Microsoft Clarity, Microsoft's free service for analyzing user behavior on websites through heatmaps and session recordings. The cookie appears when a page with the Clarity script installed is loaded, typically via the .c.clarity.ms domain, which Microsoft uses to collect and process analytics data.
It is a session cookie, meaning it only exists while the browser remains open and is automatically deleted when the browser is closed.
What data it stores
Microsoft does not publish detailed documentation on the exact format of the value stored in the SM cookie. In general, session-type Clarity cookies are used to link requests sent to Microsoft's servers to the same visit, without directly containing the user's contact information.
The collected information is transmitted to Microsoft Clarity's infrastructure (the .c.clarity.ms domain and related subdomains), where it is processed to generate heatmaps, scroll maps, and recordings of browsing sessions.
What it is used for
The main purpose of the SM cookie is to support the proper functioning of the Microsoft Clarity script during a browsing session, so that user interactions (clicks, scrolling, mouse movements) can be correctly correlated and analyzed.
For the site owner, this data helps understand how visitors actually interact with pages, identify areas of interest or points where users drop off, in order to improve user experience and conversions.
Does it require consent?
SM is classified by CookieFix under the statistics (analytics) category. Since it is used for tracking visitor behavior for analytical purposes, it is not strictly necessary for the technical operation of the site.
- Under GDPR (Regulation 2016/679) and the ePrivacy Directive, statistics cookies may be set only after obtaining the visitor's explicit consent.
- Site owners must block the Clarity script before consent is given, disclose the SM cookie and its purpose in the cookie policy, and allow consent to be easily withdrawn.
How to block or delete SM
A visitor can delete or block the SM cookie from browser settings (Chrome, Firefox, Edge, Safari), under the cookie and site data management section, or use private browsing mode to avoid longer-term storage.
For site owners, the correct approach is to use a Consent Management Platform (CMP) such as CookieFix, which automatically blocks the Microsoft Clarity script from loading until the visitor consents to the statistics category, preventing the SM cookie from being set prematurely.
Frequently asked questions
It is not a malicious cookie, but it collects data about visitor behavior for analytics purposes, which is why it falls under GDPR consent rules.
It is a session cookie, so it is automatically deleted when the visitor closes their browser.
Yes, since it is classified as an analytics cookie, it requires the visitor's prior consent under GDPR and ePrivacy, and the script must be blocked until consent is given.
You cannot remove the cookie if you actively use Microsoft Clarity, but you can control when it is set by blocking the script until consent is obtained, using a CMP like CookieFix.