eXtended Reality (XR) technologies are increasingly used in education and industry due to their support for spatial 3D interaction and contextual annotations, which enhance learning and task efficiency. Current solutions offer features like real-time collaboration and virtual annotations, but are often costly and tied to specific hardware. Key requirements for effective XR systems include device independence, usability, external data integration, and real-time collaboration. WebXR holds promise in addressing these needs, yet no comprehensive open-source platform currently exists that combines: (i) an adaptive immersive WebXR environment, (ii) remote-streaming capabilities for broader access, and (iii) integration with external 3D databases. To address this gap, we present XRidge (XR Knowledge Bridge), a cross-reality WebXR platform supporting immersive, collaborative, and data-driven experiences. XRidge is designed to be hardware-agnostic and open-source, enabling applications in remote teaching, training, and showcasing.