What is the KADUSERCOOKIE cookie?
PubMatic UserId. this identifier to identify each user uniquely. Some of the uses of this anonymous identifier are to support frequency capping, perform UID sync ups with DSP's, DMP's. DMP's / DP's push audicne data against this ID. API publishers sends this ID while making API requests to PubMatic AdServer. UAS Ad Engine also uses this cookie for FCAP purposes.
Our October 2026 scan found it on 14 sites (1% of the 2,450 we scanned), set before any consent.
- Purpose
- Advertising
- Belongs to
- PubMatic
- Set as
- Third-party (under another company's domain)
- Typical lifetime
- 12 months (vendor says: 90 days) — longer than the vendor documents
Sites that set KADUSERCOOKIE before consent
The highest-ranked 14 of 14 sites.
- elpais.com7 tracking companies
- as.com7 tracking companies
- tenki.jp27 tracking companies
- oricon.co.jp36 tracking companies
- slate.com20 tracking companies
- idnes.cz42 tracking companies
- ctvnews.ca38 tracking companies
- iqm.com14 tracking companies
- stuff.co.nz19 tracking companies
- si.com13 tracking companies
Show 4 more sites
- rediff.com42 tracking companies
- estadao.com.br19 tracking companies
- kakaku.com22 tracking companies
- atlasobscura.com28 tracking companies
Related cookies
Other cookies from PubMatic.
- pi47 sites
- KTPCACOOKIE15 sites
- chkChromeAb67Sec6 sites
- SyncRTB*6 sites
- chk5 sites
How to stop it
Declining non-essential cookies in a site's consent banner should stop KADUSERCOOKIE 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.