| Async_core | Asynchronous programming library using non-preemptive user-level threads. |
| Async_extended | Extended asynchronous programming library. |
| Async_extra | Extra async library beyond Async_core. |
| Async_unix | Async interface to unix |
| Bin_prot | Support for reading and writing OCaml-values in a type-safe binary protocol. |
| Core | Standard library overlay. |
| Core_extended | Extended core library. |
| Fieldslib | OCaml record fields as first class values. |
| Sexplib | S-expression library. |
| Type_conv | Generates code from type specifications. |
| Variantslib | OCaml variant types as first class values. |