Desktop-compatible bridge
Unity apps connect through /altws/app; test drivers connect through /altws. Messages are routed by app name and driver pairing.
npm project · open-alttester-server
Open AltTester Server
Package name: open-alttester-server on npm
Open AltTester Server is this project’s name—not a tutorial on how to launch AltTester Desktop. A free, open-source drop-in alternative to the paid AltTester Desktop app: WebSocket relay for the AltTester Unity SDK, with a real-time web dashboard for Node.js and Bun.
Why it exists
Drop-in alternative to AltTester Desktop
The AltTester Unity SDK is open source. This project replaces the paid Desktop app’s relay with a drop-in WebSocket server, CLI, and dashboard for normal developer workflows.
Node.js and Bun support
Use the same package from npm, whether your automation machines standardize on Node.js or Bun.
Live dashboard
Inspect connected Unity apps, drivers, pairings, live events, and scene hierarchy from the browser.
No clone required
Run it directly with npx open-alttester-server or bunx open-alttester-server, then point the SDK at port 13000.
Dashboard preview
AltTester Server dashboard
The browser dashboard gives local automation runs a live control surface: apps, drivers, routes, events, current scene, loaded scenes, and object tree inspection.
4
connection counters for apps, drivers, routes, and attention states
100
recent events retained in the live dashboard log
1
local server for WebSocket relay and dashboard traffic
Agent integrations
Agent-ready relay
The server exposes a local MCP endpoint for agents that support MCP clients. The GitHub skill bundle is available for agents that prefer local instructions and helper scripts, while MCP remains the shared path for Codex, Claude, Gemini, Cursor, OpenCode, Pi, and other MCP-capable tools.
Embedded MCP endpoint
Start the server and connect any MCP-capable client to the local streamable HTTP endpoint.
npx open-alttester-server http://127.0.0.1:13000/mcp
Dashboard config writer
Generate project or global MCP config for Codex, Claude, Gemini, Cursor, OpenCode, and Pi from the dashboard.
GitHub skill bundle
Codex can install skill/open-alttester-tools/ as a skill. Other agents can clone or vendor that folder, read SKILL.md, and call scripts/alttester_tools.mjs directly.
Working model
Drop it into existing tests
The server is intentionally narrow: it does the WebSocket relay job, exposes enough dashboard visibility to debug runs, and keeps existing AltTester driver code intact.
Start server
Run npx open-alttester-server. The CLI starts HTTP and WebSocket handling on port 13000 by default.
Point Unity
Configure the AltTester Unity SDK to use 127.0.0.1 and the chosen port. Device tests can use the host machine IP.
Run drivers
Keep existing Python, C#, Java, or Robot tests. Drivers connect to the server and route commands to the target app.
# install-free startup
npx open-alttester-server
AltTester Server running on port 13000
Dashboard: http://127.0.0.1:13000/
Unity apps connect to: ws://127.0.0.1:13000/altws/app
Test drivers connect to: ws://127.0.0.1:13000/altws
Unity app
AltTester SDK
->
Server
WebSocket relay
->
Driver
Python / C# / Java / Robot
Where it fits
Built for local automation loops
Use Open AltTester Server when you need a free relay instead of the paid AltTester Desktop app. Use AltTester Desktop when you need its extended productivity tooling (test recording and more).
| Need | Open AltTester Server | AltTester Desktop |
|---|---|---|
| WebSocket relay | Open-source relay for SDK apps and test drivers. | Official relay bundled with the desktop product. |
| Developer dashboard | Live local dashboard for connections, routes, events, and inspector data. | Desktop UI with additional product features. |
| Test recording | Not included. | Use AltTester Desktop for recording and advanced workflows. |
Common questions
AltTester Server FAQ
Including why the project name is not the same as “open the AltTester server” setup guides.
Is this page about “opening” AltTester Desktop?
No. Open AltTester Server is the name of this npm package (open-alttester-server), not instructions for launching AltTester Desktop. For the official Desktop app, use AltTester’s documentation. For this drop-in relay, run npx open-alttester-server.
What is an AltTester Server?
In AltTester workflows, the Desktop app runs a local WebSocket relay between the Unity SDK and your test drivers. Open AltTester Server is a free, open-source drop-in replacement for that paid Desktop relay, with a real-time web dashboard for Node.js and Bun.
Is Open AltTester Server a replacement for AltTester Desktop?
Yes, for the core relay: it speaks the same WebSocket protocol as AltTester Desktop so SDK apps and existing drivers connect without code changes. Commercial Desktop features such as UI test recording are not included.
How do I connect the AltTester Unity SDK?
Run npx open-alttester-server, then point the SDK at 127.0.0.1 and port 13000 (by default). Unity apps use /altws/app; drivers use /altws.
Does it work with Python, C#, Java, and Robot drivers?
Yes. Keep your existing AltTester driver tests; they connect to the server and route commands to the target app by name, the same way they would with AltTester Desktop.
Ready for npm
Run the relay today
Open a terminal, start the server, then point your AltTester Unity SDK build and driver tests at the same host and port.