What is the _gcl_au cookie?
Used by Google AdSense for experimenting with advertisement efficiency across websites using their services.
Our October 2026 scan found it on 336 sites (14% of the 2,450 we scanned), set before any consent.
- Purpose
- Advertising
- Belongs to
- Set as
- First-party (under the site's own domain)
- Typical lifetime
- 3 months (vendor says: 3 months) — about what the vendor documents
Sites that set _gcl_au before consent
The highest-ranked 30 of 336 sites.
- yuga.com5 tracking companies
- creativecommons.org2 tracking companies
- who.int3 tracking companies
- namecheap.com4 tracking companies
- media.net6 tracking companies
- globo.com24 tracking companies
- dropcatch.com2 tracking companies
- ivi.ru10 tracking companies
- trendmicro.com8 tracking companies
- digitalocean.com3 tracking companies
Show 20 more sites
- uol.com.br17 tracking companies
- techcrunch.com38 tracking companies
- viber.com3 tracking companies
- wps.com3 tracking companies
- oxylabs.io11 tracking companies
- airbnb.com2 tracking companies
- mailchimp.com4 tracking companies
- shopee.co.id3 tracking companies
- curseforge.com9 tracking companies
- wattpad.com3 tracking companies
- fiverr.com7 tracking companies
- ameblo.jp2 tracking companies
- allaboutcookies.org7 tracking companies
- liftoff.io6 tracking companies
- hbr.org12 tracking companies
- nbcnews.com20 tracking companies
- worldbank.org9 tracking companies
- seedtag.com4 tracking companies
- washington.edu12 tracking companies
- fidelity.com15 tracking companies
Related cookies
Other cookies from Google.
- FCCDCF141 sites
- receive-cookie-deprecation136 sites
- __Secure-YNID113 sites
- g_state92 sites
- IDE82 sites
How to stop it
Declining non-essential cookies in a site's consent banner should stop _gcl_au 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.