What is the CMID cookie?
Collects visitor data related to the user's visits to the website, such as the number of visits, average time spent on the website and what pages have been loaded, with the purpose of displaying targeted ads.
Our October 2026 scan found it on 27 sites (1% of the 2,450 we scanned), set before any consent.
- Purpose
- Advertising
- Belongs to
- Casale Media
- Set as
- Third-party (under another company's domain)
- Typical lifetime
- 12 months (vendor says: 1 day) — longer than the vendor documents
Sites that set CMID before consent
The highest-ranked 27 of 27 sites.
- amazon.com33 tracking companies
- datadoghq.com14 tracking companies
- amazon.co.za32 tracking companies
- usps.com24 tracking companies
- fidelity.com15 tracking companies
- amazon.com.mx34 tracking companies
- instructure.com17 tracking companies
- netkeiba.com20 tracking companies
- purdue.edu19 tracking companies
- nielsen.com10 tracking companies
Show 17 more sites
- slate.com20 tracking companies
- amazon.ae32 tracking companies
- xero.com18 tracking companies
- docusign.com9 tracking companies
- ynet.co.il23 tracking companies
- iqm.com14 tracking companies
- stuff.co.nz19 tracking companies
- acorns.com20 tracking companies
- zimperium.com8 tracking companies
- redcross.org16 tracking companies
- mainichi.jp30 tracking companies
- iq.com6 tracking companies
- estadao.com.br19 tracking companies
- amazon.sa32 tracking companies
- atlasobscura.com28 tracking companies
- sydney.edu.au11 tracking companies
- iii.com10 tracking companies
Related cookies
Other cookies from Casale Media.
How to stop it
Declining non-essential cookies in a site's consent banner should stop CMID 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.