What is the custom_data cookie?
Set by BidSwitch, a real-time-bidding ad exchange, to pass audience-targeting data between the advertising platforms that use it.
Our October 2026 scan found it on 22 sites (1% of the 2,450 we scanned), set before any consent.
- Purpose
- Advertising
- Belongs to
- BidSwitch
- Set as
- Third-party (under another company's domain)
- Typical lifetime
- Under a day
Sites that set custom_data before consent
The highest-ranked 22 of 22 sites.
- globo.com24 tracking companies
- terra.com.br23 tracking companies
- vnexpress.net14 tracking companies
- oricon.co.jp36 tracking companies
- haberler.com14 tracking companies
- syosetu.com24 tracking companies
- 24h.com.vn20 tracking companies
- goodreturns.in25 tracking companies
- kakuyomu.jp18 tracking companies
- chordtela.com34 tracking companies
Show 12 more sites
- politico.com31 tracking companies
- hatena.ne.jp19 tracking companies
- hindustantimes.com36 tracking companies
- asahi.com41 tracking companies
- ctvnews.ca38 tracking companies
- nicovideo.jp24 tracking companies
- myanimelist.net20 tracking companies
- japantimes.co.jp32 tracking companies
- kakaku.com22 tracking companies
- infoseek.co.jp22 tracking companies
- nifty.com32 tracking companies
- eleconomista.es24 tracking companies
Related cookies
Other cookies from BidSwitch.
How to stop it
Declining non-essential cookies in a site's consent banner should stop custom_data 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.