Microsoft Advertising UET Tag

Overview

The Microsoft Advertising Universal Event Tracking (UET) Tag is the conversion tracking pixel for Microsoft's advertising platform, which serves ads across Bing Search, the Microsoft Audience Network, Yahoo, DuckDuckGo, and other Microsoft Search partners. Advertisers place the UET Tag on their websites to measure the effectiveness of their Microsoft Advertising campaigns by tracking page views, conversions, and custom goals. The tag feeds data back to Microsoft Advertising for campaign optimization, audience targeting, and return-on-ad-spend reporting.

What This Script Does

The UET Tag loads from bat.bing.com and tracks visitor behavior on the advertiser's website.

• Script loaded: bat.bing.com/bat.js — the Universal Event Tracking script that initializes page-level tracking and reports events to Microsoft Advertising
• Page tracking: On every page load, the UET Tag fires a tracking beacon to bat.bing.com containing the page URL, referrer, page title, and visitor identifiers. This data builds the foundation for conversion attribution and audience segmentation.
• Cookies set:
  • _uetmsclkid — First-party cookie (90-day expiry). Stores the Microsoft Click ID (msclkid) from ad clicks for conversion attribution across sessions.
  • _uetsid — First-party cookie (30-minute expiry). Session identifier for correlating page views within a single visit.
  • _uetvid — First-party cookie (13-month expiry). Persistent visitor identifier for cross-session tracking and audience building.
  • MUID — Third-party cookie on bing.com (13-month expiry). Microsoft's cross-site user identifier, shared across Microsoft properties and partner sites.
• Custom events: Advertisers can configure the UET Tag to track specific conversion events (purchases, sign-ups, form submissions) by firing event beacons with revenue values, currency codes, and custom parameters.
• Remarketing: The UET Tag's visitor identifiers feed Microsoft Advertising's remarketing audiences, enabling advertisers to serve ads to previous site visitors across the Microsoft Audience Network.

Consent & Compliance

The Microsoft Advertising UET Tag falls under the marketing consent category.

Under GDPR and ePrivacy, the UET Tag requires explicit opt-in consent. It sets persistent first-party tracking cookies (_uetvid with 13-month expiry), transmits behavioral data to Microsoft's advertising servers, and the MUID third-party cookie enables cross-site user identification. This constitutes storage of non-essential cookies under the ePrivacy Directive and processing of personal data for advertising under GDPR. Microsoft Advertising supports the IAB TCF and provides consent mode integration.

Under CCPA/CPRA, the UET Tag's transmission of visitor identifiers and behavioral data to Microsoft for advertising optimization constitutes "sharing" of personal information for cross-context behavioral advertising. Advertisers must support opt-out mechanisms and honor the Global Privacy Control signal. Microsoft offers a CCPA opt-out mechanism through the Microsoft privacy dashboard.

Data transfers from the EU to the US are covered under Microsoft Corporation's EU-US Data Privacy Framework certification.

Should You Block This Without Consent?

Yes. The UET Tag sets persistent tracking cookies, transmits page-level behavioral data to Microsoft's advertising infrastructure, enables cross-site user identification through the MUID cookie, and feeds remarketing audience lists. Block the UET Tag entirely until the user grants marketing consent.