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Documentation Index

Fetch the complete documentation index at: https://docs.streampixel.io/llms.txt

Use this file to discover all available pages before exploring further.

This page covers SDK-specific communication — the JavaScript methods and event listeners exposed by pixelStreaming and emitUIInteraction.
Other ways to talk to Unreal exist:Each path has its own API. Use whichever matches the way you embed the stream.

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Sending data to UE

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UI interaction (custom JSON)

Send arbitrary JSON to UE. Primary method for custom web → UE messaging. 
appStream.stream.emitUIInteraction({
  type: 'action',
  value: 'jump'
});

appStream.stream.emitUIInteraction({
  command: 'setColor',
  color: '#ff0000',
  intensity: 0.8
});
Handle these messages in UE via the Pixel Streaming Input Component’s OnInputEvent delegate or FPixelStreamingInputHandler in C++.

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Console commands

Run UE console commands remotely: 
pixelStreaming.emitConsoleCommand('stat fps');
pixelStreaming.emitConsoleCommand('r.SetRes 1920x1080f');
pixelStreaming.emitConsoleCommand('stat unit');
Console commands run with the UE app’s permissions. Only commands that are enabled in your UE build will work — restrict which commands can be executed remotely in your build.

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Text input

Send text to UE’s currently focused text field. Mostly used in response to UE’s on-screen keyboard request: 
pixelStreaming.streamMessageController
  .toStreamerHandlers.get('TextboxEntry')?.(['Hello from the web!']);

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Receiving data from UE

Listen for custom messages sent from UE → web: 
pixelStreaming.addResponseEventListener('handle_responses', (response) => {
  const data = JSON.parse(response);

  switch (data.type) {
    case 'gameState':
      updateGameUI(data.state);
      break;
    case 'notification':
      showNotification(data.message);
      break;
  }
});
In UE, send messages with the Send Pixel Streaming Response Blueprint node or UPixelStreamingDelegates::SendPixelStreamingResponse in C++.

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On-screen keyboard

When UE requests text input via showOnScreenKeyboard, the SDK handles it automatically:
1

UE sends showOnScreenKeyboard

With the current text content and cursor position.
2

SDK shows the input modal

The built-in EditTextModal opens.
3

User confirms input

Types and submits.
4

SDK sends text back to UE

Via the TextboxEntry handler.
No code needed on your side — the SDK manages the modal and round-trip automatically.

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Round-trip example

// Web → UE: Request the score
appStream.stream.emitUIInteraction({
  type: 'request',
  action: 'getScore'
});

// UE → Web: Receive it
pixelStreaming.addResponseEventListener('handle_responses', (response) => {
  const data = JSON.parse(response);
  if (data.type === 'scoreUpdate') {
    document.getElementById('score').textContent = data.score;
  }
});

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Next

pixelStreaming API

Full reference for emitConsoleCommand, addResponseEventListener, etc.

Unreal-side blueprints

The matching UE-side setup for receiving and sending JSON.