Privacy-Preserving Attribution

Firefox Firefox Last updated: 06/13/2024 30% of users voted this helpful
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Privacy-preserving attribution (PPA) is an experimental feature shipping in Firefox version 128.

Mozilla is prototyping this feature in order to inform an emerging Web standard designed to help sites understand how their ads perform without collecting data about individual people. By offering sites a non-invasive alternative to cross-site tracking, we hope to achieve a significant reduction in this harmful practice across the web.

What is attribution?

Attribution is how advertisers learn whether their advertising works. Attribution measures how many people saw an ad on a website and then later visited the advertiser’s website to do something the advertiser cared about. For example, maybe someone sees an ad for a sale on a product, then buys that product. Attribution counts how many people do that.

Attribution is very important to advertisers. Sadly, tracking is the only way to perform attribution without help from the browser. Tracking is terrible for privacy, because it gives companies detailed information about what you do online. While Firefox includes many privacy protections that make it more difficult for sites to track you online (Enhanced Tracking Protection, Total Cookie Protection, Query Parameter Stripping, and many other measures), there’s a huge incentive for sites to find ways around these in order to perform attribution.

Our hope is that if we develop a good attribution solution, it will offer a real alternative to more objectionable practices like tracking. We are currently testing this approach to see if it can provide advertisers with the information they're looking for.

How does privacy-preserving attribution protect my data?

PPA does not involve websites tracking you. Instead, your browser is in control. This means strong privacy safeguards, including the option to not participate.

Privacy-preserving attribution works as follows:

  1. Websites that show you ads can ask Firefox to remember these ads. When this happens, Firefox stores an “impression” which contains a little bit of information about the ad, including a destination website.
  2. If you visit the destination website and do something that the website considers to be important enough to count (a “conversion”), that website can ask Firefox to generate a report. The destination website specifies what ads it is interested in.
  3. Firefox creates a report based on what the website asks, but does not give the result to the website. Instead, Firefox encrypts the report and anonymously submits it using the Distributed Aggregation Protocol (DAP) to an “aggregation service”.
  4. Your results are combined with many similar reports by the aggregation service. The destination website periodically receives a summary of the reports. The summary includes noise that provides differential privacy.

This approach has a lot of advantages over legacy attribution methods, which involve many companies learning a lot about what you do online.

PPA does not involve sending information about your browsing activities to anyone. This includes Mozilla and our DAP partner (ISRG). Advertisers only receive aggregate information that answers basic questions about the effectiveness of their advertising.

This all gets very technical, but we have additional reading for anyone interested in the details about how this works, like our announcement from February 2022 and this technical explainer.

In what conditions is privacy-preserving attribution used?

PPA is enabled in Firefox starting in version 128. A small number of sites are going to test this and provide feedback to inform our standardization plans, and help us understand if this is likely to gain traction.

PPA can be disabled in Firefox settings.

How can I disable PPA?

Firefox provides an easy simple option to disable the privacy-preserving attribution feature if users prefer not to participate. Websites will not know if you choose to opt out in this way.

To opt out, do the following:

  1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button Fx89menuButton and select Settings.
  2. In the Privacy & Security panel, find the Website Advertising Preferences section.
  3. Uncheck the box labeled Allow websites to perform privacy-preserving ad measurement.
Website advertising preferences

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