What is the khaos cookie?
Khaos is an HTTP cookie set from the .rubiconproject.com domain, belonging to Magnite (formerly Rubicon Project), one of the largest supply-side platforms (SSPs) for programmatic advertising. It is not set directly by the visited website, but by third-party scripts, iframes or bidding pixels loaded when a page displays ad slots connected to the Magnite network.
It typically appears on the first page load where programmatic ads are present, when the browser takes part in a real-time bidding auction for a banner or another ad format.
What data it stores
The cookie stores a unique identifier associated with the visitor's browser, used by Rubicon Project/Magnite's bidding system. The exact value format may vary and is not publicly documented in detail by the provider.
Data collected through this identifier is sent to Rubicon Project/Magnite servers and may be shared with other partners in the programmatic advertising chain (agencies, demand-side platforms, other SSPs) to enable bidding and delivery of relevant ads.
What it is used for
For Rubicon Project/Magnite, the khaos cookie helps recognize the browser within the programmatic advertising ecosystem, enabling participation in real-time bidding (RTB) auctions and measuring their performance.
For the website operator, this cookie supports monetization of ad slots through automated auctions, helps limit how many times the same ad is shown to the same visitor (frequency capping), and can indirectly contribute to serving ads considered more relevant to the user.
Does it require consent?
The khaos cookie falls under the marketing category (advertising/tracking). Under the ePrivacy Directive (as transposed locally, e.g. Law 506/2004 in Romania) and the GDPR, this type of cookie is not strictly necessary for the site to function, so it requires the visitor's prior, explicit and informed consent before being placed in the browser.
- The site operator must declare this cookie in the cookie policy, with its real provider, purpose and duration.
- The script that sets the cookie must be blocked until consent for the marketing category is obtained.
- Data protection authorities can sanction the placement of marketing cookies without valid consent.
How to block or delete khaos
A visitor can manually delete or block this cookie from browser settings (Chrome, Firefox, Edge, Safari), under the cookies and site data section, or use ad-blocking/anti-tracking browser extensions.
For site operators, the recommended approach is using a consent management platform (CMP) such as CookieFix, which automatically blocks marketing scripts, including those that set cookies from Rubicon Project/Magnite, until the visitor gives explicit consent for that category.
Frequently asked questions
It is not a virus or malware, but it is a tracking cookie used for programmatic advertising, meaning it can contribute to building a profile of the user's browsing behavior across multiple sites.
It appears because the site displays ads delivered through Rubicon Project/Magnite's bidding platform, integrated directly or via other ad networks or header bidding solutions.
Yes, since it is a marketing cookie, it requires the visitor's prior consent before being placed, under the ePrivacy Directive and GDPR.
It can be deleted from the browser's privacy settings, in the cookies section, by searching for the rubiconproject.com domain.