What is the SyncRTB* cookie?
Keeps list of DSP pixel Id's PubMatic synced with so far. PubMatic does userId sync up with DSP's. This cookie holds next sync up time for every pixel. Helps to maintain sync up frequency at DSP level.
Our October 2026 scan found it on 6 sites (0% 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
- 3 months (vendor says: 90 days) — about what the vendor documents
- Name
- A family of cookies: the part after SyncRTB varies by site or account.
Sites that set SyncRTB* before consent
The highest-ranked 6 of 6 sites.
- slate.com20 tracking companies
- ctvnews.ca38 tracking companies
- stuff.co.nz19 tracking companies
- rediff.com42 tracking companies
- estadao.com.br19 tracking companies
- kakaku.com22 tracking companies
Related cookies
Other cookies from PubMatic.
- pi47 sites
- KTPCACOOKIE15 sites
- KADUSERCOOKIE14 sites
- chkChromeAb67Sec6 sites
- chk5 sites
How to stop it
Declining non-essential cookies in a site's consent banner should stop SyncRTB* 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.