The subdirectories are organized as follows:

• util: Contains random unrelated utilities that don't depend on each other or the rest of the system.
• jsg: Contains magic template library for auto-generating FFI glue between C++ and V8 JavaScript.
• io: Generally contains code that handles the I/O layer which allows APIs to talk to the rest of the world. Also includes basic Worker lifecycle and event delivery.
• api: Contains implementations of publicly documented application-visible JavaScript APIs.
• server: Contains the high-level server implementation.
• tools: Contains additional meta-programs, notably a script for exporting API types.