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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.

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Overview

The frontend communicates with Unreal via the Pixel Streaming messaging system.
  • Sending → Unreal: You can send json message to your unreal engine application.
  • Receiving ← Unreal: You can listen for responses and messages coming from the Unreal side.
There are two ways to send JSON from the frontend:
  1. Via URL – pass a JSON payload in the launch URL (one-time, no frontend code required).
    • Sometimes you only need to send a message once, at the very start of the application, and not for the rest of the session.
    • To avoid building a custom frontend just for this, Streampixel lets you include a JSON message directly in the stream’s URL.
    • This is useful for one-time configuration, like setting the default map, graphics quality, or toggling UI elements when the session launches.
  2. Via WebSDK / Iframe – send JSON interactively at any point after the stream has launched.
    • If you need ongoing control — sending messages while the app is running — use our WebSDK or Iframe API.
    • This method supports unlimited, interactive communication. You can send commands in response to button clicks, toggle HUD elements, update camera views, or push live analytics at any point during the session.

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Sending messages to Unreal

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Option A: Via URL

If you only need to send a message once at the start of the application, you don’t need to create a custom frontend. You can simply include the JSON data as parameters in your stream URL.

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URL structure

https://share.streampixel.io/PROJECT_ID?fieldname=value
  • PROJECT_ID → your project identifier.
  • ? → indicates the start of parameters.
  • fieldname → the JSON key.
  • value → the data you want Unreal to receive.

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Examples

Single field 
https://share.streampixel.io/abcd1234?message=hello
Unreal Receives → { "message": "hello" }
Multiple fields 
https://share.streampixel.io/abcd1234?message=set&field=quality&value=4k
Unreal Receives → {"message": "set", "field": "quality", "value": "4k" }

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URL Generator tool

To make this easier, you can use our helper tool: https://urlgenerator.streampixel.io/ The tool automatically encodes special characters and generates a ready-to-use URL. No data is stored. Its purpose is to help you understand how URL encoding works. Even if you choose not to use the tool and create the URL manually, it will still work as long as you apply proper encoding.

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Option B: Via Iframe or WebSDK

If you need to send messages while the app is running, use the Streampixel WebSDK or Iframe API. This gives you full interactivity and unlimited control.

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Receiving messages from Unreal

When the Unreal app sends a message to the frontend, your frontend must register handlers/listeners to process it. Both the Iframe API and the WebSDK support this.

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Next steps

Unreal side - sending and receiving JSON

Set up the Unreal blueprints that consume these messages.

Frontend and application communication

See the iframe postMessage patterns in detail.