During this call, we'll refer to non-GAAP financial measures that are not prepared in accordance with Generally Accepted Accounting Principles, including adjusted EBITDA, adjusted EBITDA margin, non-GAAP operating expenses, non-GAAP net income, non-GAAP net income per diluted share and free cash flow. A reconciliation of these non-GAAP financial measures to the most directly comparable GAAP financial measure is available in the press release announcing our second quarter 2012 financial results. This press release, as well as other important content, is available in the Investor Relations section of our website, www.tripadvisor.com.
And with that, I'll now turn the call over to Steve.
Thank you, Will, and welcome, everyone to today's conference call. The second quarter completed a great first half of 2012 for TripAdvisor. We generated record quarterly revenue of $197 million and adjusted EBITDA of $97 million, continued to grow traffic and hotel shoppers while taking important steps to optimize traffic quality and continued growing and leveraging our social and mobile initiatives to drive user adoption. We're making tremendous headway on content collection, membership and traffic. At the end of Q2, we passed the 75 million reviews and opinions milestone and our travel community continues to add content at 50 contributions per minute, which translated to an accelerated pace of more than 25 million contributions for 2012. Marketable member growth, travelers whom we have permission to e-mail on a regular basis, also accelerated during the quarter, growing over 25% to more than 32 million, up over 60% year-over-year.The top of our funnel, total traffic growth, also remained strong, as Q2 comScore data reflects an average of more than 54 million worldwide unique visitors to TripAdvisor sites, up more than 31% year-over-year. Further down the funnel, hotel shoppers, the key metric for our click-based revenue line, was up approximately 30% year-over-year and would've been higher were it not for a strategy change that I'll discuss in a minute. User engagement on the site was up as well, as we saw growth in time spent per session and page views per session, according to our internal log files. We attribute this growth in user engagement to our robust email campaigns and continued efforts to personalize the site experience.