Overview

How you talk to Unreal depends on how you embed the stream. All three paths can send AND receive — they just use different APIs.

Path	Send to UE	Receive from UE
Default frontend (share URL)	URL query params: `?key=value` (one-time, at launch)	Built-in handlers — opens URLs, takes screenshots, shows keyboard, toggles cursor (see Default frontend)
Iframe `postMessage`	`iframe.contentWindow.postMessage(...)`	`window.addEventListener('message', ...)`
Web SDK	`emitUIInteraction(...)`, `emitConsoleCommand(...)`	`addResponseEventListener(...)`

Pick one based on how you embed. Don’t mix the APIs across paths — even though everything ends up in the same UE message system, the frontend-side calls are different.

Important — UE-side setup is the same

The Blueprint setup on the Unreal side is identical regardless of which frontend path you use. Set it up once and it works for URL params, iframe postMessage, and the Web SDK.

Where to read next


Unreal side	Blueprints to receive frontend messages and send your own. Shared across all three paths.
Default frontend	What the share link handles automatically, plus URL-param syntax.
Frontend side (URL params)	Detailed URL syntax for one-time messages at launch.
Iframe communication	Send and receive via `postMessage`.
Web SDK communication	The SDK’s programmatic methods and event listeners.

Use cases

JSON messaging

Reference

Important — UE-side setup is the same

Where to read next

​Important — UE-side setup is the same

​Where to read next

Important — UE-side setup is the same

Where to read next