Energy communities represent collaborative networks where individuals, local authorities, and organizations collectively produce, manage and share energy resources. To design and manage these communities, a powerful energy co-simulation tool is essential. Such a tool enables the evaluation, integration and optimization of energy in different domains, such as electrical, thermal, within virtual environments. However, current co-simulation applications are predominantly developed as command-line software kits or desktop applications requiring local installation and technical expertise, creating a substantial barrier to a wider community engagement. To address this accessibility gap, we present a web-based energy co-simulation platform. The solution relies on modern web technologies to enable sophisticated co-simulation functionalities through standard web browsers, eliminating the need for local installation and computation power.