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Cookie reference · Microsoft Clarity

The _clck cookie

The Microsoft Clarity user cookie, which keeps a site-specific Clarity user ID across visits.

_clck at a glance

Cookie name
_clck
Vendor
Microsoft Clarity
Category
Analytics
Party
First-party
Lifetime (observed)
365 daysObserved 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 _clck

What the _clck cookie does

_clck persists the Microsoft Clarity user ID and preferences for the site, so later visits from the same browser are attributed to the same Clarity user. The ID is unique to the site and isn't shared across other sites.

Microsoft's Clarity cookie list documents the purpose and that it's first-party, but has no expiry column. 1 year is the commonly reported lifetime and matches the median TagPipes observed. It's normally paired with _clsk, which handles the session.

What TagPipes observed

1.2%

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

365 days

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. _clck 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 365 days.

Often found alongside

Percentage of sites with _clck 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 _clck 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 _clck. 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.