MUID — Microsoft (Bing, Advertising)
By the OpenCookies team · published 2026-10-22 · updated 2026-10-22
- Service
- Microsoft (Bing, Advertising)
- Category
- Advertising and profiling
- Default duration
- 13 months
- Type
- Third-party cookie (set by another domain)
- Consent required?
- Yes, before any storage or reading.
What is it for?
Unique browser identifier at Microsoft, used for advertising and analytics on Bing and sites that load Microsoft tags.
What does it look like?
The value is a hexadecimal identifier of about 32 characters, written on the bing.com or clarity.ms domain.
How to see it in your browser
Open your site, press F12, then choose the “Application” tab (Chrome, Edge) or “Storage” (Firefox). This cookie is written by another domain: look for it under “Cookies”, under the service’s domain. If you cannot see it, your browser may be blocking third-party cookies.
What does the rule say?
Targeted advertising, remarketing and profiling require prior, free and informed consent. These cookies cannot be exempted.
How to prevent it before the choice
Do not load Microsoft tags (UET, Clarity) before consent.
How OpenCookies handles it
Common services like this one are in OpenCookies’ tracker list: the banner neutralizes their script before the visitor chooses and only restarts it after “Accept”. The test shows whether this cookie appears before the choice, after “Refuse” and after “Accept”.
Check it on my site
Does this cookie appear on your site before the visitor chooses? The OpenCookies test shows it in two minutes.
Related cookies
Frequently asked questions
Why is it seen with Clarity?
Because Clarity uses Microsoft identifiers to recognize the visitor.
Is it visible without third-party cookies?
Often not: browsers that block third-party cookies prevent it.
Durations are defaults and may change with configuration. This page describes a cookie; it is not legal advice.