What is the _sharedID cookie?
A shared, pseudonymous identifier from the open-source Prebid.js "SharedId" module, letting ad exchanges recognize a returning visitor across different publishers' sites during header-bidding auctions.
Our October 2026 scan found it on 10 sites (0% of the 2,450 we scanned), set before any consent.
- Purpose
- Unclassified
- Set as
- First-party (under the site's own domain)
- Typical lifetime
- 12 months
Sites that set _sharedID before consent
The highest-ranked 10 of 10 sites.
- vnexpress.net14 tracking companies
- haberler.com14 tracking companies
- aternos.org19 tracking companies
- sondakika.com9 tracking companies
- loteriasdominicanas.com14 tracking companies
- last.fm8 tracking companies
- hindustantimes.com36 tracking companies
- si.com13 tracking companies
- conectate.com.do10 tracking companies
- theweathernetwork.com21 tracking companies
How to stop it
Declining non-essential cookies in a site's consent banner should stop _sharedID 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.