Web-based memorializing is an emerging set of social practices mediated by computer networks, through which digital objects, structures, and spaces of commemoration are produced. Based on in-depth analysis of eight Web sites produced to memorialize victims of the terrorist attacks in the United States on September 11, 2001, we demonstrate that Web-based memorializing bears a diverse array of characteristics, only some of which are consistent with offline memorializing. Our analysis suggests that although Web sites produced by institutions or organizations may differ somewhat in form and content from those produced by individuals, public and private modes of memorializing observed offline are interpenetrated on the Web. Finally, we identify communal functions served and contributions to public memory made via Web-based memorializing, and propose a conceptual framework for use in future studies of Web-based memorializing practices.