_clsk — Microsoft Clarity
By the OpenCookies team · published 2026-10-22 · updated 2026-10-22
- Service
- Microsoft Clarity
- Category
- Analytics
- Default duration
- 1 day
- Type
- First-party cookie (set by your own site)
- Consent required?
- Yes, in principle: only audience measurement meeting strict conditions can be exempt from consent in the EU.
What is it for?
Groups the page views of a same session for Microsoft Clarity recordings and heatmaps.
What does it look like?
The value is a string made of several elements separated by the | sign.
How to see it in your browser
Open your site, press F12, then choose the “Application” tab (Chrome, Edge) or “Storage” (Firefox). Under “Cookies”, select your site’s address: the _clsk cookie appears in the list if present, with its value and expiry date.
What does the rule say?
Audience measurement in principle requires the visitor’s prior consent. The French CNIL accepts an exemption for some tools configured very strictly (statistical purpose only, no cross-referencing with other data and no cross-site tracking); detailed conditions are on its website.
How to prevent it before the choice
Same method as _clck: Clarity loads only after consent.
How OpenCookies handles it
Common services like this one are in OpenCookies’ tracker list: the banner neutralizes their script before the visitor chooses and only restarts it after “Accept”. The test shows whether this cookie appears before the choice, after “Refuse” and after “Accept”.
Check it on my site
Does this cookie appear on your site before the visitor chooses? The OpenCookies test shows it in two minutes.
Related cookies
_clck— Microsoft Clarity_hjSessionUser_<IDENTIFIANT>— Hotjar
Frequently asked questions
Why does it last only one day?
It is only used to group the page views of one session.
Can Clarity work without cookies?
It offers consent settings; check Microsoft’s documentation for your configuration.
Durations are defaults and may change with configuration. This page describes a cookie; it is not legal advice.