Xpra was originally just "persistent remote applications" for X11, it is now much more, supporting many platforms both as clients and servers, including a builtin HTML5 client, many protocols (SSH, UDP, VSOCK, SSL, RFB, mDNS, etc) and an unrivalled number of features: accelerated OpenGL rendering, hardware accelerated compression of graphics and audio, forwarding of webcam, printing, notifications, system trays, file transfers, drag and drop, etc