12. A method of providing third-party content based on keyword performances, comprising: identifying, by a data processing system, based on data stored in a historic online activity database, a cluster of client devices that previously performed a plurality of online activities of an online activity type in relation to a product or service context; determining, by the data processing system, based on the data stored in the historic online activity database, from a plurality of keywords, a subset of keywords associated with the plurality of online activities of the online activity type that the cluster of client devices performed in relation to the product or service context; determining, by the data processing system, a performance metric of the subset of keywords based on the plurality of online activities of the online activity type that the cluster of client devices performed in relation to the product or service context; and providing, by the data processing system, for a computing device of a third-party content provider, access to the subset of keywords and the performance metric, a parameter value determined, by the computing device of the third-party content provider, for a first keyword of the subset of keywords based on the performance metric is used to select a content item of the third-party content provider associated with the product or service context responsive to a request for third-party content, the request for third-party content indicative of the first keyword, and the selected content item is provided for display on a client device.
12. A method of providing third-party content based on keyword performances, comprising: identifying, by a data processing system, based on data stored in a historic online activity database, a cluster of client devices that previously performed a plurality of online activities of an online activity type in relation to a product or service context; determining, by the data processing system, based on the data stored in the historic online activity database, from a plurality of keywords, a subset of keywords associated with the plurality of online activities of the online activity type that the cluster of client devices performed in relation to the product or service context; determining, by the data processing system, a performance metric of the subset of keywords based on the plurality of online activities of the online activity type that the cluster of client devices performed in relation to the product or service context; and providing, by the data processing system, for a computing device of a third-party content provider, access to the subset of keywords and the performance metric, a parameter value determined, by the computing device of the third-party content provider, for a first keyword of the subset of keywords based on the performance metric is used to select a content item of the third-party content provider associated with the product or service context responsive to a request for third-party content, the request for third-party content indicative of the first keyword, and the selected content item is provided for display on a client device. 14. The method of claim 12 comprising: providing a user interface for display on the computing device of the third-party content provider, the user interface providing a list of products or services to select from; and receiving, by the data processing system, from the computing device of the third-party content provider, an indication of a selection of at least one of a product, a service, a product category and a service category representing the product or service context.