[Thread_List] returns an array of integer IDs representing every thread that is running in Lasso. These IDs can then be fed into the [Thread_Exists], [Thread_Info], and [Thread_GetPriority] tags to inspec the current state of each thread or into [Thread_Abort] or [Thread_SetPriority] to kill or alter the priority of the thread.

Each thread in Lasso represents either a browser initiated page load or an asynchronous tag or compound expression. The [Thread_List] will always include one ID which represents the current page load (also returned by [Thread_GetCurrentID]) and usually will also have IDs for the background processes in Lasso which manage the email queue, event scheduler, and session manager.

Note that since threads can be created and destroyed very quickly there is no guarantee that thread IDs listed by [Thread_List] are still running even by the time the tag has finished processing. [Thread_Exists] can be used to test whether a thread ID is still running.