Attribution is the foundation of modern advertising. It’s how businesses measure the success of their ads, tracking everything from clicks to conversions. Traditionally, this has been done using methods like cookies, fingerprinting, and similar techniques that collect detailed user data. While effective in tracking ad performance, these methods are terrible for user privacy.
Beyond privacy issues, modern attribution has become less effective due to the increased use of ad-blocking technology and policies like Apple’s ad tracking transparency feature.
Fortunately, there seems to be a new technology on the horizon that can address both of these problems at once: Privacy-Preserving Attribution.
What is Privacy-Preserving Attribution?
Privacy-Preserving Attribution (PPA) is a prototype attribution browser feature introduced by Mozilla, a company best known for its privacy-focused internet browser, Firefox.
It’s designed to help sites understand how their ads perform without collecting data about individual users. It’s a non-invasive alternative to cross-site tracking, aiming to reduce harmful practices across the web. Its unique attribute is that it operates within a browser that is in control, shifting the data collection away from websites and giving the end user more privacy safeguards, including the option to disable the feature altogether.
Mozilla’s end goal with this technology is to inform a new web standard that can be adopted by other browsers, setting a new, privacy-oriented standard for browser attribution. A crucial factor is Chrome, which has 65% of the browser market share and has broken its promise to phase out third-party cookies earlier in 2024 – a tool that forms the foundation of attribution as we know it.
Firefox may not have a large enough share of the browser market to disrupt the industry on its own, but it’s promising that they are developing this standard with a team from Meta, the leader in social media advertising, which accounted for 18% of global ad spend in 2022. Meta’s involvement is not surprising, as they reported $10 billion in losses due to Apple’s Ad Tracking Transparency feature.
When is Privacy-Preserving Attribution Coming?
Privacy-Preserving Attribution (PPA) is already live on Firefox, starting with version 128, which was first released on July 9, 2024. Currently, only a small number of sites participate in the testing phase, and this technology is not yet widely adopted.
PPA is enabled by default for all Firefox users, but you can disable the feature if you prefer not to participate.
To opt out, follow these steps:
- In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings.
- In the Privacy & Security panel, find the Website Advertising Preferences section.
- Uncheck the box labeled Allow websites to perform privacy-preserving ad measurement.

How Does Privacy-Preserving Attribution Work?
To understand how Privacy-Preserving Attribution works in detail, I recommend reading a technical explanation posted by Mozilla, but I will summarize it in simple terms below.
There are five entities participating in the process:
- User: You, the person browsing the web.
- Browser: Firefox, which handles the tracking process.
- Ad-serving website: The site where the ads are shown.
- Destination website: The site that wants to convert visitors, like making a sale.
- Aggregation service: A privacy-focused service that collects and processes data without revealing user details to ad publishers.
Here’s how the process works:
- When you visit a website showing ads (the ad-serving website), it can tell Firefox to save the fact that you saw or clicked on an ad. This information includes the ad ID and the destination website (the website the ad is promoting).
- Firefox stores this information (your ad views or clicks) in a private log for a limited time, such as 30 days. You can think of this as a big table that keeps track of the ads you’ve interacted with across all websites.
- When you later visit the destination website (like an online store) and make an action that website defined as a conversion (purchase, for example), Firefox will check its log to see if you interacted with any of that site’s ads. If it finds a match, Firefox attributes the sale to that ad.
- Instead of sending this information directly to the destination website, Firefox encrypts the report and sends it anonymously to an aggregation service.
- The aggregation service collects data, combines it, and sends a periodic report back to the destination website. This report tells the website how many conversions came from each ad, without revealing any personal user information.
By using this process, advertisers can still measure the effectiveness of their ads but cannot attribute conversions to specific users, making it a pro-privacy solution.
The Conclusion
Privacy-Preserving Attribution seems like a good thing – it promotes at least some privacy, which is good for end users and could make the internet a slightly better place.
On the flip side, Privacy-Preserving Attribution (PPA) has faced criticism. Mozilla, long seen as a champion of a free, privacy-first internet that actively blocked third-party tracking, is now introducing a form of tracking. Many view this as a shift from Mozilla’s core mission, raising concerns that PPA may compromise the values the company has long stood for.
It’s also important to note that Apple introduced a similar feature for Safari in 2019 – Privacy Preserving Ad Click Attribution (PPACA) – but it has never really gained traction, as cookies and server-side tracking provide more detailed data.
Only time will tell what the reality is, but one thing is certain: PPA is a significant topic that will remain relevant in the coming years and is worth keeping an eye on.