Useful resources for working with glTF

To inspect glTF or glb files online:

To inspect them locally:

Built-in URL parameters

Debug Flags can be appended as URL query parameters.
Use ?help to get a list of ALL parameters available.

Here are some of the most commonly used:

  • help print all available url parameter in the console
  • console opens an on-screen dev console, useful for mobile debugging
  • printGltf logs loaded gltf files to the console
  • stats shows FPS module and logs threejs renderer stats every few seconds
  • showcolliders visualizes physics colliders
  • gizmos enables gizmo rendering (e.g. when using BoxCollider or AxesHelper components)
  • and a lot more: please use help to see them all

Debug Methods

Needle Engine also has some very powerful and useful debugging methods that are part of the static Gizmos class. See the scripting documentation for more information.

Local Testing of release builds

  • First, install http-server: npm install -g http-server
  • make a build (development or production)
  • open the dist directory with a commandline tool
  • run http-server -g | -g enables gzip support
  • optional: if you want to test WebXR, generate a self-signed SSL certificateopen in new window, then run http-server -g -S to enable https (required for WebXR).


You can attach VSCode to the running local server to set breakpoints and debug your code. You can read more about debugging with VSCodeopen in new window here.

Create a launch.json file at .vscode/launch.json in your web project with the following content:

    "version": "0.2.0",
    "configurations": [
            "type": "chrome",
            "request": "launch",
            "name": "Attach Chrome",
            "url": "https://localhost:3000",
            "webRoot": "${workspaceFolder}"

If you have changed the port on which your server starts make sure to update the url field accordingly.
You can then start your local server from within VSCode:


Android Debugging

For Android debugging, you can attach Chrome Dev Tools to your device and see logs right from your PC. You have to switch your device into development mode and connect it via USB.

See the official chrome documentation hereopen in new window

  • Make sure Developer Modeopen in new window is enabled on your phone
  • Connect your phone to your computer via USB
  • Open this url in your browser chrome://inspect/#devices
  • On your mobile device allow the USB connection to your computer
  • On your computer in chrome you should see a list of open tabs after a while (on chrome://inspect/#devices)
  • Click Inspect on the tab you want to debug

iOS Debugging

For easy iOS debugging add the ?console URL parameter to get a useful on-screen JavaScript console.

If you have a Mac, you can also attach to Safari (similar to the Android workflow above).

WebXR usage and debugging on iOS requires using a third-party browser: Mozilla WebXR Vieweropen in new window.

Quest Debugging

Quest is just an Android device - see the Android Debugging section for steps.