Events and signals

Communicate through queued global events and object-scoped signals across scripting languages.

Feature status and language/platform compatibility

Choose an API to see its signature, parameters, examples and behavior.

APIs

• Events.on()
• Events.once()
• Events.connect()
• Events.emit()
• connection.disconnect()
• Events.disconnect()

Module guide

Setup and language support

These engine-owned services work in Lua 5.4, Luau, JavaScript, Python, C, C++, C#, Java, PHP, and HTML inline JavaScript. Follow Use gameplay actions to create and attach a script, install external toolchains, and choose the correct language binding. PHP and HTML scripts belong under ui/; CSS alone runs no gameplay code.

The Calls section uses JavaScript signatures. The function examples below include native syntax for all ten script types, including SDK-specific alternatives and limitations. Attach a JavaScript Object Component script to the specified target and press Play. Globals are supplied by the engine. Schedule actions from Start or a callback, rather than at script top level. Native languages use typed options and their own builder conventions; see the guide's language bindings.

Parameters

Name is the exact signal name. Callback receives payload arguments. Source is an optional stable entity ID or resolvable scene path. Payload supports booleans, finite numbers, strings/IDs, vectors and quaternions, not arbitrary nested objects.

Return and timing

On/once/connect return a connection with disconnect. Emit queues delivery during Update before the user frame callback; it never synchronously enters another language runtime.

Behavior and limitations

• The Console prints opened by followed by the owner ID on queued delivery. Once disconnects after its single delivery.
• Global on/once subscriptions are distinct from object signals. For an object signal use connect(object, name, callback) and emit(name, args, object).
• Language instances in the same play scene can communicate; no network or inter-scene transport is implied.
• Payload limits are 64 arguments, 4096 bytes per string and 16 KiB combined. The scene retains at most 4096 subscriptions and 4096 callbacks per queue.
• Destroying an object removes its scoped connections. Unrelated object destruction does not remove a global script subscription.
• Check script attachment, enabled state and the Console when an operation fails. Asynchronous errors also appear in operation state. Callback exceptions disable the owner and clean up its actions.
• Owner destruction, disable, successful reload or Stop cleans up owned actions and subscriptions. Failed reload retains the previous behavior's operations. See Operation handles for controls and lifetime details.