XKeyscore is a global NSA analytic system that allows analysts to search across vast repositories of intercepted internet content and metadata by selector — email address, phone number, IP address, or keyword. Revealed by the Guardian in July 2013 using Snowden training documents, XKeyscore was described in NSA materials as the agency's 'widest-reaching' signals intelligence analytic tool. Analysts could query billions of records covering email, chat, browsing history, and search queries without prior court approval for individual searches.