What is the SRM_B cookie?
This cookie is used by Microsoft Advertising to uniquely identify web browsers across websites and track user behavior for personalized ad delivery.
Table of Contents
About SRM_B
| Vendor | Microsoft |
|---|---|
| Cookie Domain | c.bing.com |
| Category Category The functional category of the technology, such as Web Analytics or Social Media. Learn more | Advertising & Paid Media |
| Consent Category Consent Category The consent category this cookie most commonly falls under across sites we scan, normalized into four standard categories. Learn more | Targeting & Advertising |
| Prevalence | Very Common |
| Popularity Popularity Popularity is calculated from our dataset of 4.5B+ cookies analyzed across hundreds of millions of web pages. Learn more | Found on 11.3% of scanned pages |
| Expiration Type | Timestamp |
| Expiration Duration | 24 days |
| Party Type Party Type Whether the cookie is first-party or third-party. Learn more | 3rd-Party |
| Risk Level Risk Level Rates how sensitive the data stored by this cookie is (High, Medium, or Low) based on data classification and distribution. Learn more | High |
| Vendor Privacy Policy | https://privacy.microsoft.com/en-us/privacystatement |
| Vendor Website | https://www.microsoft.com |
What is the purpose of SRM_B?
The SRM_B cookie is a third-party tracking cookie placed via Microsoft's c.bing.com domain by Microsoft Advertising (formerly Bing Ads) tags, frequently in conjunction with Microsoft's cookie-syncing flow toward c.clarity.ms. It functions as a persistent identifier that enables Microsoft to recognize a specific browser across different websites that have integrated Microsoft tracking tags. This cross-site synchronization allows the vendor to gather analytical data about visitor behavior, evaluate the effectiveness of advertising campaigns, and attribute ad conversions.
Ultimately, the collected data enables Microsoft to associate a browser with its advertising and analytics systems and deliver personalized, targeted advertisements across its advertising network based on browsing behavior. The cookie value is a hexadecimal-encoded unique identifier (e.g., 0B9FF97C635A6E612876EE36629D6F80).
What are the Privacy Risks of SRM_B?
Risk Level: High
This cookie serves as a persistent, cross-site tracking identifier. By synchronizing user IDs across multiple domains, it allows Microsoft to monitor a user's behavior across the internet, track their interactions with different websites, and build detailed profiles for targeted advertising. This level of behavioral profiling, combined with the sharing of a uniquely identifiable value with a major third-party ad network (Microsoft Advertising), poses a high privacy risk.
How to Remove SRM_B from a Website
Because SRM_B is set by Microsoft's advertising/analytics technology, a website administrator removes it by removing the Microsoft tag(s) that place it - specifically the Microsoft UET (Universal Event Tracking) / Bing Ads tracking tag and, where present, the Microsoft Clarity script - from the site's source code or from the tag management system (e.g., Google Tag Manager) that deploys them. This cookie is integral to those Microsoft services and cannot be selectively disabled while keeping the tag running; the only reliable way to stop it being set is to remove the underlying Microsoft Advertising / Clarity integration from the site entirely. If the organization needs to retain the integration but stop this cookie, it would have to discontinue use of the feature with Microsoft, as there is no documented vendor configuration that suppresses this specific identifier while the tag remains active.