FairThreads offers a very simple framework for concurrent and parallel programming . Basically, it defines schedulers which are synchronization servers, to which threads can dynamically link or unlink. All threads linked to the same scheduler are executed in a cooperative way, at the same pace, and they can synchronize and communicate using broadcast events. Threads which are not linked to any scheduler are executed by the OS in a preemptive way, at their own pace. FairThreads offers programming constructs for linking and unlinking threads.

FairThreads is fully compatible with the standard Pthreads library and has a precise and clear semantics for its cooperative part; in particular, systems exclusively made of threads linked to one unique scheduler are actually completely deterministic. Special threads, called automata, are provided for short-lived small tasks or when a large number of tasks is needed. Automata do not need the full power of a native thread to execute and thus consume less resources.