This API measures ad conversions (e.g. purchases) and attributes them to clicked ads without using cross-site persistent identifiers like third-party cookies. Note that this is a very early stage design, and we’re explicitly not asking for permission to ship yet. We would like to get initial feedback on the idea and start prototyping. This API is in Origin Trial from Chrome 86 through Chrome 97


Currently, the web ad industry measures conversions via identifiers they can associate across sites. These identifiers tie information about which ads were clicked to information about activity on the advertiser's site (the conversion). This allows advertisers to measure ROI, and for the entire ads ecosystem to understand how well ads perform. Since the ads industry today uses common identifiers across advertiser and publisher sites to track conversions, these common identifiers can be used to enable other forms of cross-site tracking. This doesn’t have to be the case, though, especially in cases where identifiers like third party cookies are either unavailable or undesirable. A new API surface can be added to the web platform to satisfy this use-case without them, in a way that provides better privacy to users.



Specification link

Unknown standards status - check spec link for status

Status in Chromium


Origin trial (tracking bug)

Consensus & Standardization

After a feature ships in Chrome, the values listed here are not guaranteed to be up to date.

  • No signal
  • Negative
  • Positive


Intent to Prototype url

Intent to Prototype thread


When third-party origin trials are shipped, we intend to add support for them in this experiment. The standard API flow involves two different top-level origins, and in many cases the API is leveraged by a common third party on both of these sites. By allowing third party scripts to enable the trial, this will greatly decrease the burden on developers to enable the origin trial on all necessary sites.

Last updated on 2021-12-13