Task Library - Now Available!

Hey developers,

We have just enabled a brand new library that you can use in your projects. The task library allows you to talk directly with our engine’s task scheduler to manage and schedule code. It features a number of new methods as well as some improvements to existing methods.



Takes a thread or function and resumes it immediately through the engine’s scheduler. Additional arguments are passed to the thread or function being resumed.

void task.spawn(function | thread, ...args)

This is particularly useful when calling a function which may yield when iterating over a set of objects:

local function playerAdded(player)

for _, player in ipairs(Players:GetPlayers()) do
    task.spawn(playerAdded, player)

task.spawn is based on the fastSpawn pattern rather than being a replacement for spawn. We recommend you use this method where you would otherwise use fastSpawn.


Takes a thread or function and defers it until the next resumption cycle at which point it is resumed with the engine’s scheduler. Additional arguments are passed to the thread or function being resumed.

void task.defer(function | thread, ...args)

You should typically use this when you want similar behavior to task.spawn but don’t care about the thread running immediately.

task.defer(print, "A")
--> B
--> A

task.defer is an improved version of spawn which schedules a thread to be resumed as soon as possible (but not immediately) without any throttling.


Takes a thread or function and schedules it for resumption after the given amount of time has elapsed on the next Heartbeat step. The thread is resumed with built-in error handling and support for other engine features. Any additional arguments are passed to the thread or function being resumed.

void task.delay(duration, function | thread, ...args)

Since the actual delay time may vary it can be calculated by passing the current time as an argument.

task.delay(2, function (scheduledTime)
    print(os.clock() - scheduledTime) --> 2.038702
end, os.clock())

A duration of zero will result in the thread or function being resumed on the next step.

task.delay is an improved version of delay which schedules a thread to be resumed after some time has elapsed without throttling.


Yields the current thread until the given duration (in seconds) has elapsed and then resumes the thread on the next Heartbeat step.

elapsed task.wait(duration=0)

Since the actual yield time may vary, this method returns it for convenience.

local elapsedTime = task.wait(2) -- wait for 2 seconds
print(elapsedTime) --> 2.0792941

If no duration is given the duration will default to zero meaning the thread will automatically resume on the next step.

-- is equivalent in behavior to

task.wait is an improved version of wait which schedules the current thread to be resumed after some time has elapsed without throttling.

Existing Methods

We will eventually mark the existing methods (spawn, delay, and wait) as deprecated in favor of their alternatives however they will continue to work as they do now for the foreseeable future and we have no plans to change this.

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This topic was automatically opened after 7 minutes.

Super excited to get these in my projects already. The task APIs look super easy to use, introduce to novice developers and get them used to new patterns. I too look forward to adopting new patterns in my code involving them. This could also help very much with getting used to deferred events which I initially resisted heavily.

:heart: the improved versions of old functions that were particularly discouraged (e.g. delay), especially wait and how it’s based on Heartbeat frequency. Don’t have to write my own boilerplate for that anymore or abuse Promises to get what I need. Same goes with task.spawn for fastSpawn. Less boilerplate and I can use these better versions rather than the ones based on the old frequencies.

Outstanding work. Thank you, engineers!

Also, alas begone, legacy wait. Get outta here.



Is task.wait() with no parameters an alternative to using RunService.Heartbeat:Wait()?

There was this article about not using wait() with no parameters.

Or should we continue using RunService.Heartbeat:Wait()?


Yes, task.wait() is now equivalent to RunService.Heartbeat:Wait(), and a lot more convenient too. The amount of time spent typing that out saved is astonishing…


Is there any reason you didn’t just change the default behaviours of those functions, and instead add a new task library? Does this have something to do with parallel lua :flushed:

Anway’s glad that useless old function has now been given a replacement


I believe this should answer your question:

The reason using wait() with no parameters is bad is because it (task.wait()) is


i’m wondering if this wait() alternative:

function Halt(Duration)
	--// Arguments: (Duration[Number])
	Duration = (Duration or 0)
	local cur = 0;
	if (Duration <= 0) then
	while cur < Duration do
		cur += Heartbeat:Wait();
	return cur;

is the same as:


(post withdrawn by author, will be automatically deleted in 1 hour unless flagged)


It should be noted that results of these aren’t equivalent:


task.wait()'s DeltaTime result will count from the time of the call, while Heartbeat:Wait() will count from the previous Heartbeat.

Also, task.delay() causes a crash instead of an error.


Is this almost like some kind of task manager for Studio?


Because you can’t do Heartbeat:Wait(2) since :Wait() function on RBXScriptSignals doesn’t take any arguments?


What is the fastSpawn pattern?


So what’s the difference of task.wait, task.spawn, and wait, spawn?


I’m still struggling to understand use cases for task.defer. I understand how it works and how it fits into the library but under what circumstances would you want code to run at some predetermined point later in time that you have no control over? Is there any real benefit in doing so?

I also don’t understand this. How is it not a replacement for spawn? And wasn’t the original fastspawn method implemented with BindableEvents? With deferred events that would mean that it wouldn’t be an immediate resumption, unless of course I’m misinterpreting the meaning of “fastSpawn pattern”.


deferred on Nevermore (originally fastSpawn)

“An expensive way to spawn a function. However, unlike spawn(), it executes on the same frame, and unlike coroutines, does not obscure errors.”

(edit: changed link to folder with README, was originally set to a release branch)


I assume for legacy purposes, old games experiences whose behavior could be compromised if they just redo the old functions.


Will documentation for task happen soon? I’d expect it to be available on the developer hub for more info and on task scheduler article on availability of a class (aka today).


Hmmm… what is happening??

Is this basically like coroutine? I mean, I am a builder, not knowing much about these, but isn’t it the same thing?


Updated my “Spawn is Evil” article to just point to the new task library. Glad that this problem finally has an easy solution that doesn’t require several paragraphs to explain!