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At DuckDuckGo, we don’t track you, ever. That’s our privacy policy in a nutshell. For example, we do not create unique cookies and, more generally, architect our product so that we do not even have the ability to create a search or browsing history for any individual — it’s privacy by design.

At the same time, we need a way to reliably improve our products for our users in an anonymous way. There are a few methods we’ve developed to achieve this.

First, you might notice that when you search DuckDuckGo, there may be an “&atb=” URL parameter in the web address at the top of your browser. This parameter allows us to anonymously A/B (split) test product changes we make to DuckDuckGo. For example, users in the A group would get blue links and users in the B group would get red links, and we’d be able to measure how usage of DuckDuckGo is impacted by different color links. For some experiments, we may need to ensure a consistent user experience across additional pages after you interact with a page element. In those cases, we may store non-personal data using local storage (e.g., the large and generalized user experience group you’re in), but only after your first interaction, only on your device, and never by default.

Second, we measure engagement of specific events on the page (e.g. when a misspelling message is displayed, and when it is clicked). This allows us to run experiments where we can test different misspelling messages and use CTR (click through rate) to determine the message’s efficacy. If you are looking at network requests, these are the ones going to the one-pixel image at These requests are anonymous and the information is used only by us to improve our products.

Third, you may notice similar atb.js or exti requests made by our browser extensions and mobile apps. These requests help us anonymously count how many devices are using an experience. For example, our browser extensions and mobile apps will send an atb.js request with each search made. These requests allow us to count approximately how many devices accessed DuckDuckGo without knowing anything about those devices or the exact searches they made.

Fourth, for certain elements in our search pages you may notice the &vis parameter being used in requests. This parameter allows us to measure usefulness by identifying which elements were actually visible on a page or received an interaction like hovering. Because of different screen sizes, visibility can be very different across devices (e.g., desktop vs. mobile vs. tablet). As users click on these elements, we use this interaction data to measure conversions effectively. The parameter values are anonymous, grouped together in batches, and are devoid of any personally identifiable information.

All of these requests are all fully encrypted in transit to DuckDuckGo, such that nobody else but us can see them. And like with all other requests to DuckDuckGo, there is no personally identifiable information embedded in them, and we do not store IP addresses associated with them.

To be clear, this means we cannot ever tell what individual people are doing since everyone is anonymous, and that is a limit of our statistical methods since we are private by design. We can, however, within this anonymous limitation, reliably determine what changes are generally working, using these anonymous methods.

We have developed these systems from scratch, instead of using third-party services, because of our privacy promise to never collect or share any personal information. We’re proud to be able to improve our site for you in a completely anonymous way!

If you have any concerns, please feel free to contact us.

Prior versions on GitHub.