What is the __zlcmid cookie?
__zlcmid is an HTTP cookie set by Zendesk, specifically by the Zendesk Chat (formerly Zopim) component embedded in many customer support and live chat widgets. It appears on a site once that site loads the Zendesk chat/support widget for visitors.
The cookie is created by the Zendesk script as soon as the widget loads on the page, and it persists for its typical lifetime of about one year, regardless of whether the visitor starts a conversation.
What data it stores
__zlcmid stores a unique identifier generated for the current visitor, which Zendesk uses to recognize them on later visits. The value is an alphanumeric string that does not directly contain readable personal information.
Data associated with this identifier is sent to Zendesk's servers to link sessions and any chat conversations back to the same visitor.
What it is used for
The main purpose is chat continuity: if a visitor returns to the site or moves between pages, Zendesk can recognize them as the same person and preserve conversation context or widget preferences (such as whether the chat window is open or closed).
For the site owner, this cookie enables the support widget to work correctly, but it is not required for the site's core functionality.
Does it require consent?
CookieFix classifies __zlcmid as a preferences (functional) cookie. Under GDPR and the ePrivacy Directive (2002/58/EC, transposed in Romania via Law 506/2004), cookies in this category are not strictly necessary for the site to function, so they generally require prior visitor consent before being set.
- Site owners should list this cookie in their cookie policy, including its purpose and duration.
- The Zendesk widget (and therefore __zlcmid) should ideally load only after the visitor accepts the preferences/functional category, rather than by default on page load.
How to block or delete __zlcmid
A visitor can manually delete or block __zlcmid from their browser's site data/cookie settings by locating the domain associated with the Zendesk widget. Removing it resets chat session recognition on the next visit.
For site owners, automatic blocking until consent is typically handled by a CMP such as CookieFix, which prevents the Zendesk script from loading (and __zlcmid from being set) until the visitor accepts the preferences/functional category.
Frequently asked questions
It's a cookie set by Zendesk's live chat widget, used as a visitor identifier across sessions.
Yes, since it's classified as preferences/functional, it should only be set after the visitor gives consent, not automatically on page load.
Its typical duration is about one year, though this can vary depending on the site's Zendesk configuration.
Zendesk will no longer recognize the visitor on their next visit, and the context of a previous chat conversation may be lost.