Attention: Here be dragons

This is the latest (unstable) version of this documentation, which may document features not available in or compatible with released stable versions of Godot.


Inherits: RefCounted < Object

A unit of execution in a process.


A unit of execution in a process. Can run methods on Objects simultaneously. The use of synchronization via Mutex or Semaphore is advised if working with shared objects.

Note: Breakpoints won't break on code if it's running in a thread. This is a current limitation of the GDScript debugger.


To ensure proper cleanup without crashes or deadlocks, when a Thread's reference count reaches zero and it is therefore destroyed, the following conditions must be met:




get_id ( ) const


is_alive ( ) const


is_started ( ) const


start ( Callable callable, Priority priority=1 )


wait_to_finish ( )


enum Priority:

Priority PRIORITY_LOW = 0

A thread running with lower priority than normally.


A thread with a standard priority.

Priority PRIORITY_HIGH = 2

A thread running with higher priority than normally.

Method Descriptions

String get_id ( ) const

Returns the current Thread's ID, uniquely identifying it among all threads. If the Thread has not started running or if wait_to_finish has been called, this returns an empty string.

bool is_alive ( ) const

Returns true if this Thread is currently running the provided function. This is useful for determining if wait_to_finish can be called without blocking the calling thread.

To check if a Thread is joinable, use is_started.

bool is_started ( ) const

Returns true if this Thread has been started. Once started, this will return true until it is joined using wait_to_finish. For checking if a Thread is still executing its task, use is_alive.

Error start ( Callable callable, Priority priority=1 )

Starts a new Thread that calls callable.

If the method takes some arguments, you can pass them using Callable.bind.

The priority of the Thread can be changed by passing a value from the Priority enum.

Returns @GlobalScope.OK on success, or @GlobalScope.ERR_CANT_CREATE on failure.

Variant wait_to_finish ( )

Joins the Thread and waits for it to finish. Returns the output of the Callable passed to start.

Should either be used when you want to retrieve the value returned from the method called by the Thread or before freeing the instance that contains the Thread.

To determine if this can be called without blocking the calling thread, check if is_alive is false.

Note: After the Thread finishes joining it will be disposed. If you want to use it again you will have to create a new instance of it.