Overview
The Microsoft Ads Universal Event Tracking (UET) tag is a JavaScript snippet that tracks user behaviour on a website and sends conversion and audience data to Microsoft's advertising platform (formerly Bing Ads). UET enables conversion tracking, remarketing list creation, and automated bidding optimisation across the Microsoft Search Network, which includes Bing, Yahoo, and DuckDuckGo syndicated results. The UET tag is frequently deployed alongside Google Ads tags but receives less governance attention despite collecting comparable data. Microsoft's broad enterprise presence means the UET tag is commonly found on regulated organisation websites, particularly in financial services and public sector contexts.
Detection Capabilities
- Signature count
- 2
- Detection methods
- network
Performance Impact
Performance Impact
- Script size
- 30 KB
- Requests per page
- 2
Common Mistakes
- 1 Treating the UET tag as lower-risk than Google or Meta advertising tags when it collects comparable browsing and conversion data requiring the same consent controls
- 2 Not enabling Microsoft's consent mode integration, which allows the tag to respect CMP signals and operate in a reduced data collection mode when consent is denied
- 3 Deploying UET via a tag manager without restricting it to the advertising consent category, allowing it to fire before the user has granted consent
- 4 Failing to review the auto-tagging behaviour that appends click identifiers (msclkid) to landing page URLs, which can persist personal data in server logs
- 5 Overlooking UET during cookie audits because Microsoft's first-party cookies (_uetmsclkid, _uetvid) are less well-known than Google or Meta equivalents
Compliance Considerations
The UET tag sets first-party cookies (_uetmsclkid, _uetvid, _uetsid) and transmits browsing behaviour to Microsoft servers in the United States. Under GDPR, this requires explicit advertising consent. Microsoft is self-certified under the EU-US Data Privacy Framework, providing a legal basis for transatlantic data transfers. Microsoft's consent mode integration allows UET to operate in a restricted mode when consent is not granted, but organisations must verify this is correctly configured with their CMP. The UET tag should be categorised under advertising consent and blocked until explicit consent is obtained. Organisations in regulated sectors should pay particular attention to the auto-tagging feature, as msclkid parameters in URLs may be logged by web servers and constitute personal data under GDPR.
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