What is the _pubcid cookie?
A shared, pseudonymous identifier from the open-source Prebid.js "Publisher Common ID" module, letting ad exchanges recognize a returning visitor across different publishers' sites during header-bidding auctions.
Our October 2026 scan found it on 15 sites (1% of the 2,450 we scanned), set before any consent.
- Purpose
- Advertising
- Set as
- First-party (under the site's own domain)
- Typical lifetime
- 6 months
Sites that set _pubcid before consent
The highest-ranked 15 of 15 sites.
- elmundo.es20 tracking companies
- terra.com.br23 tracking companies
- oricon.co.jp36 tracking companies
- syosetu.com24 tracking companies
- snaptik.app2 tracking companies
- trilltrill.jp23 tracking companies
- animanch.com22 tracking companies
- vlr.gg12 tracking companies
- primis.tech11 tracking companies
- politico.com31 tracking companies
Show 5 more sites
- thedailybeast.com18 tracking companies
- bostonglobe.com10 tracking companies
- japantimes.co.jp32 tracking companies
- searchenginejournal.com8 tracking companies
- infoseek.co.jp22 tracking companies
How to stop it
Declining non-essential cookies in a site's consent banner should stop _pubcid 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 written by CookieTosser, for a cookie the Open Cookie Database doesn't cover.
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.