Control the Elgato Prompter from the command line — display power, brightness, contrast, and flip — by talking to Elgato Camera Hub's local control API.

The Prompter is driven as a display, and Camera Hub has no built-in hotkey or Stream Deck action for turning that display on and off. This gives you a scriptable one: bind prompter toggle to a Stream Deck key, a shortcut, or a home-automation trigger.

Camera Hub exposes a JSON-RPC 2.0 interface over a local WebSocket — the same interface its own Stream Deck plugin uses. This tool connects to that API on 127.0.0.1 and reads or sets Prompter properties (getSupportedPrompterProperties / setPrompterProperty).

Camera Hub must be running. These are undocumented internal methods, so behavior may change between Camera Hub versions; the property IDs are pinned in src/client.mjs and easy to update.

• macOS (or wherever Camera Hub runs) with Elgato Camera Hub installed and running
• An Elgato Prompter connected
• Node.js 22+ (uses the built-in WebSocket — no runtime dependencies)

npm install -g prompter-ctl

Or run without installing:

npx prompter-ctl status

Or clone and link for development:

git clone https://github.com/benbalter/prompter-ctl
cd prompter-ctl
npm link

prompter                 # print "on" or "off" (same as `status`)
prompter on              # turn the Prompter display on
prompter off             # turn the Prompter display off
prompter toggle          # flip the Prompter display power
prompter brightness 80   # set brightness (30–100)
prompter contrast 44     # set contrast (1–100)
prompter properties      # dump every supported Prompter property as JSON
prompter --help          # full usage
prompter --version       # print version

Exit codes: 0 success · 1 command sent but new state not confirmed · 2 Camera Hub unreachable · 3 usage error.

The client is also usable as an ES module:

import { PrompterClient } from "prompter-ctl";

const prompter = await PrompterClient.connect();
console.log(await prompter.isEnabled()); // true | false
await prompter.setEnabled(false);        // turn the display off
prompter.close();

See PrompterProperty for the known property IDs (ENABLED, BRIGHTNESS, CONTRAST, HORIZONTAL_FLIP, MODE).

Camera Hub's own plugin can adjust Prompter brightness and flip, but not display power. To bind power to a key, point a System → Open action (or a small wrapper app) at prompter toggle. Because Stream Deck launches actions without your shell environment, use an absolute path to node and to the CLI, and make sure Camera Hub is running first.

Tests run against a mock Camera Hub — no hardware needed. They use ws for the mock server:

npm install
npm test

Property IDs and methods were derived by observing Camera Hub's own, publicly-reachable local interface — no decompilation of Elgato software. If a Camera Hub update changes them, PRs updating src/client.mjs are welcome. Please keep contributions clean-room: protocol facts only, never code or assets copied from Elgato/Corsair software.

This is an independent, unofficial tool. It is not affiliated with, authorized by, maintained by, sponsored by, or endorsed by Elgato or Corsair Memory, Inc. "Elgato", "Prompter", "Camera Hub", and "Stream Deck" are trademarks of their respective owners and are used here solely for nominative, descriptive purposes (to identify the hardware and software this tool interoperates with).

The tool talks only to Camera Hub's own local API on your own machine (127.0.0.1) — the same interface Camera Hub's Stream Deck plugin uses. It implements an interoperable client from observed protocol behavior; it does not copy, decompile, or redistribute any Elgato/Corsair code, and it circumvents no access control or license mechanism.

Provided "as is", without warranty of any kind. You are responsible for your own use, including compliance with any applicable software license or terms for Elgato Camera Hub. See LICENSE.

MIT © Ben Balter