MSCLKID, short for Microsoft Click ID, is a unique code that Microsoft Advertising adds to the end of your landing page address each time someone clicks one of your ads, so that a conversion later on can be matched back to that exact click. In your browser it appears as ?msclkid= followed by a long string of letters and numbers.
How MSCLKID works
When Microsoft Click ID auto-tagging is switched on in the account settings, every ad click carries its own ID to your site. Microsoft’s Universal Event Tracking (UET) tag, its equivalent of the Google tag, reads the ID from the address and, with the visitor’s consent, stores it in a first-party cookie called _uetmsclkid. When that visitor later submits a form or completes a purchase, the UET tag reports the conversion with the stored ID, and Microsoft credits the ad, keyword and campaign that produced the click.
It is the same idea as Google’s GCLID, and it serves the same second purpose. If you capture the MSCLKID in a hidden form field and save it in your CRM with the enquiry, you can upload the sale weeks later as an offline conversion. That tells Microsoft which clicks became paying customers, not just which became form fills.
Microsoft keeps the click ID separate from a second option that appends UTM tags to your URLs. The click ID feeds Microsoft’s own conversion tracking; UTM parameters are what GA4 and most other analytics tools read to label the traffic. Many accounts have one switched on and not the other.
Why it matters
Plenty of UK advertisers run Microsoft Advertising alongside Google Ads, often by importing their Google campaigns, because it reaches searchers on Bing and on Microsoft’s partner search sites, an audience Google Ads does not cover. The import copies keywords, ads and budgets, but the click ID, the UET tag and the conversion goals still have to be set up properly. When they are not, Microsoft reports clicks and spend with few or no conversions, and its automated bid strategies have nothing to learn from.
Consent adds a UK-specific step. The _uetmsclkid cookie is not strictly necessary, so PECR requires consent before it is stored. At the time of writing (October 2026), Microsoft expects advertisers with visitors in the UK, the EEA and Switzerland to pass consent signals to UET through its consent mode, so the tag behaves according to what the visitor chose on your banner. If the banner is not connected to UET, the tag either sets its cookie without permission or loses conversions it could legitimately have recorded.
Common mistakes
- Redirects that strip the query string. A redirect from http to https, from a non-www address or from an old landing page can drop everything after the question mark, taking the click ID with it.
- Auto-tagging on, UET missing. The ID arrives on the page, but no tag is there to store it or report the conversion.
- Relying on MSCLKID in GA4. GA4 needs UTM tags to label Microsoft ad traffic reliably; without them, paid clicks can be reported as organic Bing visits or end up in the wrong channel.
- Not capturing it on forms. If the ID is not saved with each enquiry, offline conversion uploads are impossible later.
- Setting UET cookies before consent. Storing the _uetmsclkid cookie before the visitor has made a choice on your banner breaches PECR.
How to act on it
In Microsoft Advertising, confirm under account-level settings that Microsoft Click ID auto-tagging is on, and decide whether to let Microsoft add UTM tags too. Then test the journey without paying for a click: open your landing page with ?msclkid=test123 on the end, follow any redirects, and check the parameter is still there when the page loads. Accept marketing cookies and confirm the _uetmsclkid cookie appears in your browser’s developer tools.
If your sales happen offline or over the phone, add a hidden field to each enquiry form that captures the ID, and make sure your CRM keeps it. Finally, confirm your consent banner sends its signals to UET as well as to Google’s tags. Setting up and checking this tracking across Google and Microsoft is part of the performance marketing work I do before scaling any paid search budget.