If you are developing for older or Symbian (S60) devices, you need the legacy SDKs (Software Development Kits).
Whether you are looking to relive the glory days of the 3310 or you are an engineer needing to test complex network configurations, there is a "Nokia simulator" for you. Since Nokia’s ecosystem ranges from vintage handsets to modern 5G infrastructure, the installation process depends entirely on what you are trying to simulate. 1. For Retro Enthusiasts: Old Nokia Handset Simulators nokia simulator online install
If you are comfortable with coding/DevOps and want a fast, text-based way to simulate topologies, Nokia officially supports . This is not a GUI "online" tool, but it is the modern way to simulate Nokia SROS. If you are developing for older or Symbian