What is the _clsk cookie?
Connects multiple page views by a user into a single Microsoft Clarity session recording.
Table of Contents
About _clsk
| Vendor | Microsoft |
|---|---|
| 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 | Performance & Analytics |
| 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 11.7% of scanned pages |
| Expiration Type | Timestamp |
| Expiration Duration | 1 day |
| Party Type Party Type Whether the cookie is first-party or third-party. Learn more | 1st-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 | Medium |
| Vendor Privacy Policy | https://privacy.microsoft.com/en-us/privacystatement |
| Vendor Website | https://www.microsoft.com/ |
What is the purpose of _clsk?
The _clsk cookie is a first-party cookie set by the Microsoft Clarity analytics script. Its primary technical function is to link sequential page views made by the same user into a unified session recording. The cookie stores a pseudonymous identifier allowing the Clarity platform to track the user's continuous journey, including mouse movements, clicks, scrolls, and other interactions across multiple pages on the website. This data is then used by site administrators to generate behavioral insights, heatmaps, and session replays.
What are the Privacy Risks of _clsk?
Risk Level: Medium
The _clsk cookie functions as an analytics session identifier that links page views into a continuous recording of the user's interactions (including clicks, scrolls, and mouse movements). Although it is restricted to the first-party context and uses a pseudonymous ID, the underlying technology collects granular behavioral data that can be considered a privacy risk depending on the website's content, placing it at a Medium risk level.
How to Remove _clsk from a Website
Because _clsk is set directly by the Microsoft Clarity tracking script, the only way for a website operator to fully eliminate it is to remove the Clarity setup/tracking script from the site's source code (or tag manager), which disables Clarity entirely. If the operator wants to keep Clarity but stop it from writing this cookie, Clarity provides a project-level setting (Settings > Setup > Advanced) to turn off cookie usage; with cookies disabled Clarity no longer sets _clsk (each page view is then treated as a separate session rather than being stitched together). There is no way to remove _clsk while leaving the Clarity script running with its default cookie behavior enabled.