"Apple is famously restrictive about confining third party apps to their sandboxes. That Apple doesn’t allow background processes is well-known, and Apple rejects apps that attempt to read the various databases and media folders directly. So it’s a bit surprising that Apple supports a form of inter-process communication (IPC) using URL protocol handlers. In this post, I’ll show how Alocola — our open source, Apple approved, in the App Store, Safari location helper — uses URL protocol handlers for IPC to work alongside Safari." - Graham Sergeant