Attribution in the Browser: Who Benefits from Mozilla/Google/Meta's Ad Standard

Attribution in the Browser: Who Really Benefits from Google and Meta’s New Privacy Standard – James O'Claire

Google, Meta and the unlikely addition of Mozilla are teaming up to work on a browser W3 specification that would add browser user agent features to track impression, click data and ‘conversion’ data. This data is then sent to respective parties

Ad Impression → Ad Networks<br>Conversions → Advertiser

So far this is just a duplication of what is naturally tracked by each party, ie just their own resources. The difference then is that this data is forwarded by each party to an attribution service provider (Google/Meta/Mozilla) who aggregates and returns conversion histograms to the Ad network:

Ad Impression → Browser Function → Ad Network → Attribution Provider<br>Conversion → Browser Function → Advertiser → Attribution Provider

At first glance, this would nearly seem like any expected flow of ad data, but here the "Advertiser" seems to stand in for the Ad Network , working on behalf of the advertiser. Why? Because otherwise the owner of the site would need to manage the attribution selection and call measureConversion() along with then updating the Ad Network.

So what realistically will happen? Ad networks will require JS pixels to be dropped on the advertisers site to manage the measureConversion and attribution process.

So the real process:<br>Ad Impression → Browser → Ad Network → Attribution Provider<br>Conversion → Browser → Ad Network (via pixel on advertiser site) → Attribution Provider

Firstly, this mostly seems to be a fix for situations where Cookies are removed.

How is this problematic for users? As a user I do not mind when an advertiser (eg Nike) tracks what blog I came from to Nike website. My concern is a Meta / Google that tracks every site I was on and went to. So in this way, I think advertisers and users should be aligned.

Could MMPs Stand by Benefit?

Mobile attribution is based on device fingerprinting. While MMP companies like AppsFlyer (45% app market share) are not mentioned, there could be some potential for MMPs to work on behalf of an mobile advertiser to call measureConversion() and gather attribution from mobile web to app that is *not* just fingerprinting. AppsFlyer has recently released web2app which, despite the hype, has the usual probabilistic and short lookback windows for deferred deep link installs. MMPs would have a strong desire to move from probabilistic to something more deterministic.

The problem? The usual, what’s always kept mobile and digital ad measurement separate. A WebView opened by the advertiser app does not have access to the device regular browser cookies.

Given that mobile operating systems are run by the ad networks Apple and Google respectively, you could see this some change here if the browser Attribution API comes to pass. Still they would likely have a hard time carving out a space for MMPs to stay between the ad network and advertiser.

The local way?

The API has the potential to support small web publishers but the danger that this is simply co-opted by the ad monopolies to consolidate their positions is real. With the idea of browser tracking ads, why not move the whole process into the local browser, completely cutting out the server calls until a conversion is recorded? This is a popular idea but would add potential avenues for ad fraud where a saveImpression() can be called locally where the ad network ecosystem wide resources to realize this is likely a fraudulent impression would be lacking.

I think there is room there for other fraud fighting models to help, but the obvious threat of this type of fraud will likely keep a completely local attribution model from being developed for now.

The current compromise

This leads to the current W3 spec and where we are now. I see real positives and negatives to the suggested specs. I’ll be keeping an eye on it in the coming weeks to months (deadline is November 2026 for the working group to finish) and see how it develops, or if this gets added to the Privacy Sandbox graveyard.

Attribution in the Browser: Who Benefits from Mozilla/Google/Meta's Ad Standard

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