Hackaday

NPAPI (Netscape Plugin API) allowed browsers to execute native code as plugins, offering capabilities that modern alternatives like WebAssembly and JavaScript cannot fully replicate. Key advantages include direct UDP socket access, local network adapter information, and straightforward rendering to screen surfaces. While most browsers dropped NPAPI support citing security concerns, browsers like Pale Moon still support it. The technology involves exporting specific functions (NP_, NPP_, NPN_ prefixed) from shared libraries, with initialization, destruction, and scriptable interfaces. Much NPAPI documentation has been erased from the web, requiring archive.org for reference materials and sample code.

NPAPI And The Hot-Pluggable World Wide Web