What is the MC cookie?
Tracking of users and measure and improve performance and supports personalisation.
Our October 2026 scan found it on 3 sites (0% of the 2,450 we scanned), set before any consent.
- Purpose
- Advertising
- Belongs to
- Quantcast
- Set as
- First-party on 33% of sites, third-party on 67%
- Typical lifetime
- 13 months (vendor says: 13 months) — about what the vendor documents
Sites that set MC before consent
The highest-ranked 3 of 3 sites.
- fidelity.com15 tracking companies
- toyota.com19 tracking companies
- redcross.org16 tracking companies
How to stop it
Declining non-essential cookies in a site's consent banner should stop MC 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.