What is the _uetvid cookie?
_uetvid is an HTTP cookie placed by Microsoft Advertising's (formerly Bing Ads) Universal Event Tracking (UET) script, when a site has the UET tag installed for conversion tracking or remarketing.
It appears as soon as the UET script loads and runs on the page, regardless of whether the visitor interacted with a Bing ad — it's enough for the site to have the tag installed.
What data it stores
The cookie stores a unique identifier associated with the visitor, used by Microsoft to recognize them on later visits to the same site or other sites running the UET tag from the same account or related accounts within the same audience network.
The exact value format is not publicly documented in detail; data collected through UET (including this identifier) is sent to Microsoft/Bing domains for processing and reporting in Microsoft Advertising.
What it is used for
The main purpose is long-term conversion tracking (identifying who saw or clicked a Bing ad and later returned to the site for a relevant action) and building remarketing audiences for future campaigns.
For the site owner, this cookie underlies the performance reports in Microsoft Advertising and enables ad budget optimization based on actual visitor behavior.
Does it require consent?
_uetvid is classified as a marketing cookie (advertising/tracking). Under the ePrivacy Directive (as implemented in EU member states) and GDPR, this type of cookie requires the visitor's explicit, prior consent before being set.
- The site owner must disclose it in the cookie policy, including the provider (Microsoft), purpose, and duration.
- The UET script must not load before consent is obtained for the marketing category.
- Data protection authorities can sanction sites that set such cookies without prior consent.
How to block or delete _uetvid
A visitor can manually delete or block _uetvid from browser settings (Chrome, Firefox, Edge, Safari — cookie and site data management section), or use ad-tracking blocking extensions.
For site owners, the correct approach is to prevent the UET script from running at all before consent. A consent management platform like CookieFix automatically blocks the UET script (and other marketing tags) until the visitor explicitly accepts the marketing category, avoiding premature setting of the _uetvid cookie.
Frequently asked questions
Yes, as a marketing/tracking cookie, it requires the visitor's explicit, prior consent under GDPR and the ePrivacy rules.
_uetvid is the long-term visitor identification cookie, lasting about 13 months, while _uetsid is the session cookie, lasting a few hours, used to track a single visit.
The typical duration is about 13 months from the last time it was set or renewed, per Microsoft Advertising's practice.
Microsoft Advertising will no longer be able to recognize the visitor on return visits, which affects conversion measurement and remarketing targeting for that site's Bing campaigns.