Overview
Bidr is the cookie-syncing and audience matching domain operated by RhythmOne (now part of Tremor International, which rebranded to Nexxen). It facilitates identity resolution and cookie synchronisation across demand-side platforms, supply-side platforms, and data management platforms in the programmatic advertising ecosystem. Bidr tags appear on websites through programmatic ad supply chains, header bidding wrappers, and third-party advertising pixels, often without the website operator's direct knowledge. The bidr.io domain is one of the most frequently flagged third-party tracking domains in cookie audits of European websites, making it a common finding in governance reviews of regulated organisations.
Detection Capabilities
- Signature count
- 1
- Detection methods
- network
Performance Impact
Performance Impact
- Requests per page
- 1
Common Mistakes
- 1 Not being aware that bidr.io cookies and requests are present on the website because they were introduced through programmatic supply chain partners rather than direct deployment
- 2 Failing to block bidr.io cookie syncing before advertising consent is obtained, as header bidding scripts may load Bidr as a secondary dependency without explicit tag manager configuration
- 3 Not including bidr.io in the cookie declaration because it appears as an unfamiliar third-party domain that is difficult to attribute to a specific vendor
- 4 Assuming that blocking the primary advertising tag is sufficient when Bidr's cookie syncing may persist through other supply chain paths
- 5 Not assessing the scope of cross-platform identity resolution performed by Bidr, which links user identifiers across multiple advertising platforms
Compliance Considerations
Bidr (Nexxen/RhythmOne) sets third-party cookies and performs cross-platform cookie synchronisation that constitutes personal data processing under GDPR, requiring explicit advertising consent. The cookie syncing process shares user identifiers across multiple advertising platforms, which amplifies the privacy impact. Bidr's presence on a website often indicates broader programmatic supply chain exposure that should be audited comprehensively. Under the ePrivacy Directive, third-party cookie syncing clearly requires consent. Organisations should audit their programmatic advertising stack for Bidr domains, ensure all supply chain partners are covered by the CMP advertising consent category, and include bidr.io in their cookie declaration. Nexxen processes data in the United States and should be assessed against EU-US Data Privacy Framework requirements.
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