Cloud computing has emerged as a solution for large-scale online service applications that require intense processing, storage and networking capabilities. Cross-cloud communication framework (C3F) was proposed to enable intercommunication among clouds in order to share computing resources. For testing of C3F requires simulation of multiple clouds simultaneously. Although, many cloud simulators are available but multiple cloud simulation under different policies and administrations is not supported. This paper discusses the development of CloudWeb that is a web-based prototype for simulation of multiple clouds concurrently. CloudWeb is developed using open source technologies.