The test_cookie cookie
A 15-minute Google cookie on doubleclick.net that checks whether the browser accepts cookies at all.
test_cookie at a glance
- Cookie name
test_cookie- Vendor
- DoubleClick
- Category
- Functional
- Party
- Third-party
- Typical duration
- 15 minutes
- Set on
.doubleclick.net- Value format
- A fixed string, commonly CheckForPermission (format not documented by vendor)
- Name match
- Exactly
test_cookie
What the test_cookie cookie does
Google's ad servers set test_cookie on doubleclick.net to check whether the browser accepts cookies from that domain. If it can be written and read back, other doubleclick.net cookies such as IDE can be used. It doesn't carry a user identifier.
Google documents the domain, a 15 minute lifetime and a functionality purpose. The check-for-cookie-support mechanic is well established but not described on Google's page. Seeing it is a reliable sign that a Google advertising tag loaded from doubleclick.net.
What TagPipes observed
0.91%
of sites scanned set it (373 of 41,162)
under an hour
median observed lifetime
TagPipes scanned 41,162 public websites between August 11, 2026 and September 13, 2026, loading up to three pages per site in a real browser as a first-time visitor. test_cookie was present on 373 of them.
It was set as a first-party cookie on 0 sites and as a third-party cookie on 373. A site can count in both. Where it was stored as a persistent cookie, the median lifetime we recorded was under an hour.
Often found alongside
Percentage of sites with test_cookie where the other cookie was also present.
Technologies detected on the same sites
- Google Analytics on 94% of them (55% of all sites scanned)
- Google Ads on 92% of them (12% of all sites scanned)
- Google Fonts on 83% of them (78% of all sites scanned)
- Google Tag Manager on 62% of them (30% of all sites scanned)
- DoubleClick on 55% of them (11% of all sites scanned)
Aggregate figures across all sites scanned. Websites of TagPipes customers are excluded, no individual site is named, and cookie values are never read or stored. Snapshot dated September 13, 2026.
How to check for test_cookie on a website
- Open the site in Chrome, then open DevTools (F12, or Cmd+Option+I on a Mac).
- Go to the Application tab and expand Cookies in the left panel.
- Select each domain listed there and look for
test_cookie. The Expires column shows when it will be deleted. - If it is not there, reload the page. Many cookies are only set after a tag has loaded, and some only after a visitor has made a consent choice.
Other DoubleClick cookies
Sources
Purpose, duration and value format checked against the vendor documentation above on . The figures under What TagPipes observed are TagPipes scan data from September 13, 2026, not values documented by the vendor. Vendors change their cookies, and sites can configure their own names and lifetimes. Browse all cookies.
Know every cookie your own site sets
TagPipes Pulse identifies the cookies dropped on your site and flags unclassified or miscategorized ones. Shield builds your cookie declaration from a real scan rather than a questionnaire.
TagPipes monitors, configures and reports. It does not determine legal compliance and does not provide legal advice. Output is informational and reflects observed state at the time of observation. Rawsoft's expertise is technology, not law; please confirm any regulatory interpretation with your own counsel.