It has been nearly twenty years since section 512 of the Digital Millennium Copyright Act established the so-called notice and takedown process. Despite its importance to copyright holders, online service providers, and Internet speakers, very little empirical research has been done on how effective section 512 is for addressing copyright infringement, spurring online service provider development, or providing due process for notice targets.This report includes three studies that draw back the curtain on notice and takedown: 1. using detailed surveys and interviews with more than three dozen respondents, the first study gathers information on how online service providers and rightsholders experience and practice notice and takedown on a day-to-day basis;2. the second study examines a random sample from over 100 million notices generated during a six-month period to see who is sending notices, why, and whether they are valid takedown requests; and3. the third study looks specifically at a subset of those notices that were sent to Google Image Search. The findings suggest that whether notice and takedown “works” is highly dependent on who is using it and how it is practiced, though all respondents agreed that the Section 512 safe harbors remain fundamental to the online ecosystem. Perhaps surprisingly in light of large-scale online infringement, a large portion of OSPs still receive relatively few notices and process them by hand. For some major players, however, the scale of online infringement has led to automated, “bot”-based systems that leave little room for human review or discretion, and in a few cases notice and takedown has been abandoned in favor of techniques such as content filtering. The second and third studies revealed surprisingly high percentages of notices of questionable validity, with mistakes made by both “bots” and humans.The findings strongly suggest that the notice and takedown system is important, under strain, and that there is no “one size fits all” approach to improving it. Based on the findings, we suggest a variety of reforms to law and practice.