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Java in combination with Web browsers' abilities to load and execute untrusted Java applets in a secure fashion has made computing over the Web a possibility. Now the challenge is to fully utilize this potential, given the limitations imposed by browsers. This paper presents Knitting-Factory, an infrastructure to facilitate Web-based computing, which addresses this challenge. It supports building distributed applications, specifically those consisting of Java applets executing in browsers. It is composed of (1) a distributed name service to assist users in locating other participants of a distributed computation via standard browsers, (2) an embedded class server to eliminate the need for external HTTP servers for serving applet code, and (3) a technique for direct applet-to-applet communication.In this paper, we describe the design and implementation of KnittingFactory and demonstrate its benefits by applying it to three distinct areas of Web-based computing. First, we apply our distributed name service to a client/server architecture to enable RMI clients to locate servers on unknown hosts. Second, we use the embedded class server to extend the capability of Charlotte, a parallel computing environment. And finally, we build a collaborative application using our direct applet-to-applet communication technique which does not require a forwarding agent. Metacomputing on theWeb: The projects which focus on Java-based parallel computing include ATLAS [1], Charlotte [3], JPVM [11], JavaParty [22], Javelin [8], ParaWeb [6], and WebFlow [5]. Similarly, there have been proposals for Web-enabled virtual machines as a base for High Performance Computing and Communication (HPCC) platform [14], to use Java in an SPMD programming model [17], and to extend Java with global pointers and remote service request mechanisms from the Nexus communication library [13]. Unfortunately, all but Charlotte and Javelin fail to take advantage of Web browsers in bringing distributed computing to every-day users.JPVM provides a message passing interface to Java stand-alone applications, but not applets. Projects such as JavaParty and [17] require running a Java process to server