Source: Roblox Creator Hub · CC BY 4.0 · View source · Code samples: MIT Imported 2026-10-03. Formatting adapted for this site.
MessagingService
Inherits from: Instance → Object
MessagingService allows servers of the same experience to communicate with each other in real time, typically within 1-2 seconds, using topics. Topics are developer‑defined strings (1–80 characters) that servers use to send and receive messages.
Delivery is best effort and not guaranteed. Make sure to architect your experience so delivery failures are not critical.
Cross-Server Messaging explores how to communicate between servers in greater detail.
If you want to publish ad-hoc messages to live game servers, or publish across experiences, you can use the Open Cloud APIs.
Limitations
Note that these limits are subject to change.
| Limit | Maximum |
|---|---|
| Size of message | 1kB |
| Messages sent per game server | 600 + 240 * (number of players in this game server) per minute |
| Messages received per topic | (40 + 80 * number of servers) per minute |
| Messages received for entire game | (400 + 200 * number of servers) per minute |
| Subscriptions allowed per game server | 20 + 8 * (number of players in this game server) |
| Subscribe requests per game server | 240 requests per minute |
Inherits from: Instance
Memory category: Instances
Tags: NotCreatable, Service, NotReplicated
Methods
| Name | Type / Returns | Description |
|---|---|---|
| MessagingService:PublishAsync | () | Invokes the supplied callback whenever a message is pushed to the topic. |
| MessagingService:SubscribeAsync | RBXScriptConnection | Begins listening to the given topic. |
Inherited from Instance
| Name | Type / Returns | Description |
|---|---|---|
| Instance:AddTag | () | Applies a tag to the instance. |
| Instance:children | Instances | Returns an array of the object's children. |
| Instance:ClearAllChildren | () | This method destroys all of an instance's children. |
| Instance:Clone | Instance | Create a copy of an instance and all its descendants, ignoring instances that are not Archivable. |
| Instance:clone | Instance | |
| Instance:Destroy | () | Sets the Instance.Parent property to nil, locks the Instance.Parent property, disconnects all connections, and calls Destroy() on all children. |
| Instance:destroy | () | |
| Instance:FindFirstAncestor | Instance? | Returns the first ancestor of the Instance whose Instance.Name is equal to the given name. |
| Instance:FindFirstAncestorOfClass | Instance? | Returns the first ancestor of the Instance whose Object.ClassName is equal to the given className. |
| Instance:FindFirstAncestorWhichIsA | Instance? | Returns the first ancestor of the Instance for whom Object:IsA() returns true for the given className. |
| Instance:FindFirstChild | Instance? | Returns the first child of the Instance found with the given name. |
| Instance:findFirstChild | Instance | |
| Instance:FindFirstChildOfClass | Instance? | Returns the first child of the Instance whose ClassName is equal to the given class name. |
| Instance:FindFirstChildWhichIsA | Instance? | Returns the first child of the Instance for whom Object:IsA() returns true for the given className. |
| Instance:FindFirstDescendant | Instance? | Returns the first descendant found with the given Instance.Name. |
| Instance:GetActor | Actor? | Returns the Actor associated with the Instance, if any. |
| Instance:GetAttribute | Variant | Returns the value which has been assigned to the given attribute name. |
| Instance:GetAttributeChangedSignal | RBXScriptSignal | Returns an event that fires when the given attribute changes. |
| Instance:GetAttributes | Dictionary | Returns a dictionary of the instance's attributes. |
| Instance:GetChildren | Instances | Returns an array containing all of the instance's children. |
| Instance:getChildren | Instances | |
| Instance:GetDebugId | string | Returns a coded string of the debug ID used internally by Roblox. |
| Instance:GetDescendants | Instances | Returns an array containing all of the descendants of the instance. |
| Instance:GetFullName | string | Returns a string describing the instance's ancestry. |
| Instance:GetStyled | Variant | Returns the styled or explicitly modified value of the specified property, or else the default property value if it hasn't been styled/modified. |
| Instance:GetStyledPropertyChangedSignal | RBXScriptSignal | Returns an event that fires when the given style property changes on the instance. |
| Instance:GetTags | Array | Gets an array of all tags applied to the instance. |
| Instance:HasTag | boolean | Check whether the instance has a given tag. |
| Instance:IsAncestorOf | boolean | Returns true if an Instance is an ancestor of the given descendant. |
| Instance:IsDescendantOf | boolean | Returns true if an Instance is a descendant of the given ancestor. |
| Instance:isDescendantOf | boolean | |
| Instance:IsPropertyModified | boolean | Returns true if the value stored in the specified property is not equal to the code-instantiated default. |
| Instance:QueryDescendants | Instances | Returns an array containing all descendants of the instance that match the selector string. |
| Instance:Remove | () | Sets the object's Parent to nil, and does the same for all its descendants. |
| Instance:remove | () | |
| Instance:RemoveTag | () | Removes a tag from the instance. |
| Instance:ResetPropertyToDefault | () | Resets a property to its default value. |
| Instance:SetAttribute | () | Sets the attribute with the given name to the given value. |
| Instance:WaitForChild | Instance | Returns the child of the Instance with the given name. If the child does not exist, it will yield the current thread until it does. |
Inherited from Object
| Name | Type / Returns | Description |
|---|---|---|
| Object:GetPropertyChangedSignal | RBXScriptSignal | Get an event that fires when a given property of the object changes. |
| Object:IsA | boolean | Returns true if an object's class matches or inherits from a given class. |
| Object:isA | boolean |
MessagingService:PublishAsync
This function sends the provided message to all subscribers to the topic, triggering their registered callbacks to be invoked.
Yields until the message is received by the backend.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| topic | string | Determines where the message is sent. | |
| message | Variant | The data to include in the message. |
Returns
| Type | Description |
|---|---|
| () |
| Field | Value |
|---|---|
| tags | ["Yields"] |
| security | None |
| thread safety | Unsafe |
| capabilities | ["ServerCommunication"] |
MessagingService:SubscribeAsync
This function registers a callback to begin listening to the given topic. The callback is invoked when a topic receives a message. It can be called multiple times for the same topic.
Callback
The callback is invoked with a single argument, a table with the following entries:
| Field | Summary |
|---|---|
| Data | Developer supplied payload |
| Sent | Unix time in seconds at which the message was sent |
It yields until the subscription is properly registered and returns a connection object.
To unsubscribe, call Disconnect() on the returned object. Once called, the callback should never be invoked. Killing the script containing the connections also causes the underlying connect to be unsubscribed.
See also MessagingService:PublishAsync() which sends the provided message to all subscribers to the topic, triggering their registered callbacks to be invoked.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| topic | string | Determines where to listen for messages. | |
| callback | Function | Function to be invoked whenever a message is received. |
Returns
| Type | Description |
|---|---|
| RBXScriptConnection | Connection that can be used to unsubscribe from the topic. |
| Field | Value |
|---|---|
| tags | ["Yields"] |
| security | None |
| thread safety | Unsafe |
| capabilities | ["ServerCommunication"] |
Code samples: View on Creator Hub (subscribing-to-cross-server-messages).
Properties
Inherited from Instance
| Name | Type / Returns | Description |
|---|---|---|
| Instance.Archivable | boolean | Determines if an Instance and its descendants can be cloned using Instance:Clone(), and can be saved/published. |
| Instance.archivable | boolean | |
| Instance.Capabilities | SecurityCapabilities | The set of capabilities allowed to be used for scripts inside this container. |
| Instance.IsInSandbox | boolean | Indicates whether the instance is inside a sandboxed container. |
| Instance.Name | string | A non-unique identifier of the Instance. |
| Instance.Parent | Instance | Determines the hierarchical parent of the Instance. |
| Instance.PredictionMode | PredictionMode | Reflects the client-side prediction mode applied to the instance under server-authoritative physics. |
| Instance.RobloxLocked | boolean | A deprecated property that used to protect CoreGui objects. |
| Instance.Sandboxed | boolean | When enabled, the instance can only access abilities in its Capabilities list. |
| Instance.UniqueId | UniqueId | A unique identifier for the instance. |
Inherited from Object
| Name | Type / Returns | Description |
|---|---|---|
| Object.ClassName | string | A read-only string representing the class this Object belongs to. |
| Object.className | string |
Events
Inherited from Instance
| Name | Type / Returns | Description |
|---|---|---|
| Instance.AncestryChanged | Fires when the Instance.Parent property of this object or one of its ancestors is changed. | |
| Instance.AttributeChanged | Fires whenever an attribute is changed on the Instance. | |
| Instance.ChildAdded | Fires after an object is parented to this Instance. | |
| Instance.childAdded | ||
| Instance.ChildRemoved | Fires after a child is removed from this Instance. | |
| Instance.DescendantAdded | Fires after a descendant is added to the Instance. | |
| Instance.DescendantRemoving | Fires immediately before a descendant of the Instance is removed. | |
| Instance.Destroying | Fires immediately before (or is deferred until after) the instance is destroyed via Instance:Destroy(). | |
| Instance.StyledPropertiesChanged | Fires whenever any style property is changed on the instance, including when a property is set to nil. |
Inherited from Object
| Name | Type / Returns | Description |
|---|---|---|
| Object.Changed | Fires immediately after a property of the object changes, with some limitations. |