What is the SRM_B cookie?
Collected user data is specifically adapted to the user or device. The usercan also be followed outside of the loaded website, creating a picture of the visitor's behavior.
Our October 2026 scan found it on 11 sites (0% of the 2,450 we scanned), set before any consent.
- Purpose
- Functional
- Belongs to
- Bing / Microsoft
- Set as
- First-party on 9% of sites, third-party on 91%
- Typical lifetime
- 13 months (vendor says: 1 year) — about what the vendor documents
Sites that set SRM_B before consent
The highest-ranked 11 of 11 sites.
- bing.com0 tracking companies
- msn.com4 tracking companies
- oxylabs.io11 tracking companies
- tailscale.com7 tracking companies
- cmu.edu6 tracking companies
- crunchyroll.com4 tracking companies
- ssl.com9 tracking companies
- aarp.org30 tracking companies
- guard.io14 tracking companies
- reolink.com11 tracking companies
Show 1 more site
- coxautoinc.com10 tracking companies
Related cookies
Other cookies from Bing / Microsoft.
- MUID38 sites
- ASP.NET_SessionId23 sites
- _uetsid22 sites
- _uetvid21 sites
- MR16 sites
How to stop it
Declining non-essential cookies in a site's consent banner should stop SRM_B being set on later visits. Blocking third-party cookies in your browser settings stops the third-party kind everywhere, and clearing cookies for a site removes any it already set.
Description from the Open Cookie Database (Apache 2.0).
Understanding this page
- How cookie lifetimes work, and why a 13-month _ga matters
What a cookie's "expires" field actually controls, why Google Analytics ships a 2-year default that many sites cut down to 13 months, and how Safari's 7-day cap on script-set cookies changes the picture.
- First-party vs third-party cookies (and why "first-party" still tracks you)
What the distinction actually means technically, why browsers only block one of the two, and how CNAME cloaking, server-side tagging and cookies like _ga let sites keep tracking under their own domain.
- How to block or limit trackers
Browser privacy settings, content blockers, Global Privacy Control and clearing cookies compared honestly — what each one actually stops, what it doesn't, and what it costs you in return.