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Cookie reference · Microsoft Clarity

The _clsk cookie

The Microsoft Clarity session cookie, which stitches several page views into one session recording.

_clsk at a glance

Cookie name
_clsk
Vendor
Microsoft Clarity
Category
Analytics
Party
First-party
Lifetime (observed)
1 dayObserved median across TagPipes scans. The vendor does not document a lifetime, so this is not its configured value.
Set on
.<your-domain>
Value format
String (internal structure not documented by vendor)
Name match
Exactly _clsk

What the _clsk cookie does

_clsk connects multiple page views by one visitor into a single Microsoft Clarity session. It holds the current session reference so each page load is appended to the same recording rather than starting a new one.

Microsoft documents the purpose and that it's a first-party cookie, but not its lifetime. 1 day is the commonly reported figure and matches the median TagPipes observed.

What TagPipes observed

1.2%

of sites scanned set it (477 of 41,162)

1 day

median observed lifetime

TagPipes scanned 41,162 public websites between August 11, 2026 and September 13, 2026, loading up to three pages per site in a real browser as a first-time visitor. _clsk was present on 477 of them.

It was set as a first-party cookie on 449 sites and as a third-party cookie on 30. A site can count in both. Where it was stored as a persistent cookie, the median lifetime we recorded was 1 day.

Often found alongside

Percentage of sites with _clsk where the other cookie was also present.

Technologies detected on the same sites

  • Microsoft Clarity on 100% of them (1.4% of all sites scanned)
  • Google Analytics on 96% of them (55% of all sites scanned)
  • Google Tag Manager on 78% of them (30% of all sites scanned)
  • Google Fonts on 77% of them (78% of all sites scanned)
  • Meta Pixel on 58% of them (13% of all sites scanned)

Aggregate figures across all sites scanned. Websites of TagPipes customers are excluded, no individual site is named, and cookie values are never read or stored. Snapshot dated September 13, 2026.

How to check for _clsk on a website

  1. Open the site in Chrome, then open DevTools (F12, or Cmd+Option+I on a Mac).
  2. Go to the Application tab and expand Cookies in the left panel.
  3. Select each domain listed there and look for _clsk. The Expires column shows when it will be deleted.
  4. If it is not there, reload the page. Many cookies are only set after a tag has loaded, and some only after a visitor has made a consent choice.

Other Microsoft Clarity cookies

Sources

Purpose and value format checked against the vendor documentation above on . The observed lifetime and the figures under What TagPipes observed are TagPipes scan data from September 13, 2026, not values documented by the vendor. Vendors change their cookies, and sites can configure their own names and lifetimes. Browse all cookies.

Know every cookie your own site sets

TagPipes Pulse identifies the cookies dropped on your site and flags unclassified or miscategorized ones. Shield builds your cookie declaration from a real scan rather than a questionnaire.

See Pulse See Shield

TagPipes monitors, configures and reports. It does not determine legal compliance and does not provide legal advice. Output is informational and reflects observed state at the time of observation. Rawsoft's expertise is technology, not law; please confirm any regulatory interpretation with your own counsel.