ComScore takes up the three-year contract to report on online, video and mobile audiences beginning in January, when Nielsen’s three-year deal concludes.

UKOM began tendering for the new contract last June – half way through Nielsen’s term. Five agencies pitched, including ComScore and Nielsen.

ComScore lost out to Nielsen last time, with UKOM owners and stakeholders plumping for Nielsen’s panel-based approach to measuring online audiences. ComScore had pitched a hybrid approach, combining panel and server-side data, which Nielsen is now in the process of implementing with UKOM. The official launch of hybrid measurement data is set for late-May.

The UK win caps recent successes in Spain and the Netherlands for ComScore. All together, the three European markets represent €1.7bn in online display advertising. CEO Magid Abraham said: “We are pleased with this recognition of our commitment to the region and endorsement of our continued investment and innovation in digital audience measurement.”

UKOM is jointly owned by the Association of Online Publishers and the Internet Advertising Bureau, with a governing board including representatives of ISBA and the Institute of Practitioners in Advertising.

ISBA’s director of media affairs Bob Wootton said: “Advertisers need measurement that makes sense and is easier to compare across other marketing channels. We are excited to see the new measurement capabilities ComScore will deliver in 2013.”