Gifs and memes (Kaplan and Nova, 2016), “buzz” on the Web and social networks are inherent to digital cultures since the very first steps of the Web (i.e., Godwin’s Law, Dancing babies, Hamster Dance, cf. McGrath, 2019). Virality has developed and changed over time, may it be related to forms (macro images, videos, etc.) and platforms (YouTube, 4Chan, Twitter, TikTok, etc.), audiences, curation and dissemination (with features encouraging spreadability within social platforms), etc., while relying on some patterns that were identified by Shifman (2014), Milner (2018), Jenkins (2009) and others. However, history and diachronic approaches still remain underrepresented in studies of online virality, although Finn Brunton’s Spam, Jason Eppink’s visual history of gifs (2014), or the Memes entry in The Sage Handbook of Web History (McGrath, 2019) can be mentioned. Historicizing virality through times, spaces and platforms is at the heart of the Hivi project at C2DH, University of Luxembourg (https://hivi.uni.lu). While starting to historicize these “Internet phenomena”, may it be Numa Numa Guy, Leave Britney Alone, Grumpy Cat, the Harlem Shake, Distracted Boyfriends, etc., challenges related to sources become more and more obvious: researchers have to deal with ephemerality as well as data overload, with several spaces of heritagization on the live and archived web, with gaps, silences and noises, issues of searchability in web archives, etc. This presentation focused on a case study, the Harlem Shake, to first demonstrate the variety of sources and spaces (physical and digital) that may be used to retrieve and rebuild this phenomenon (i.e., press, audiovisual content, archived web in several institutions, live web and platforms, etc.). It then presented the challenges related to this kind of reconstruction that is also strongly intertwining vernacular and commercial cultures; sound, video, textual contents; local as well as international spaces, etc.