# How to install Tampermonkey and a script for debugging WebRTC

## Installing Tampermonkey

To run user scripts in Chrome, it is convenient to use the extension **Tampermonkey**.

Go to the Chrome Web Store and install the extension:

{% embed url="<https://chromewebstore.google.com/detail/tampermonkey/dhdgffkkebhmkfjojejmpbldmpobfkfo>" %}

After installation, click the extensions icon in the top right and pin it **Tampermonkey**.

{% hint style="info" %}
The extension is only needed to run the script in the browser. By itself, it does not eliminate WebRTC leaks.
{% endhint %}

## How to add the script manually

For this guide, use the script from the Gist:

* [WebRTC debug script](https://gist.github.com/Kr1tos/26585898c08e5222d5edc3d6fad546be)

{% stepper %}
{% step %}
**Open the Gist with the script**

Follow the Gist link.

Open the file with the script and copy its entire contents.
{% endstep %}

{% step %}
**Create a new script in Tampermonkey**

Click the icon **Tampermonkey** and select **Create a new script**.

Delete the default template that opens in the editor.
{% endstep %}

{% step %}
**Paste the script code**

Paste the copied code from the Gist into the Tampermonkey editor.

Save the changes with the keyboard shortcut **Ctrl + S** or the button **File → Save**.
{% endstep %}

{% step %}
**Check that the script is enabled**

Make sure the new script appears in the Tampermonkey list and is in the status **Enabled**.
{% endstep %}
{% endstepper %}

## How to check that the script is working

1. Make sure the switch for the script is enabled.
2. Refresh the desired page.
3. Open DevTools via **F12**.
4. Go to the **Console**.
5. It is convenient to filter output by tags `\[TM]`, `\[WebRTC]` and `\[NET]`.

### What logs should appear

Right after the script starts, service messages usually appear:

```
[TM] Network hooks installed
[TM] WebRTC hook installed
```

If the page creates `RTCPeerConnection`, WebRTC logs will appear in the console:

```
[WebRTC] created
config: { iceServers: [...] }
ICE servers: [...]
```

During candidate gathering, local and remote candidates will be visible:

```
[WebRTC] local candidate raw: candidate:...
[WebRTC] local candidate parsed: { ip: "192.168.1.10", port: "52344", type: "host" }

[WebRTC] remote candidate raw: candidate:...
[WebRTC] remote candidate parsed: { ip: "185.123.45.67", port: "3478", type: "srflx" }
```

If the connection reaches route selection, the script will show the final path:

```
[WebRTC] SELECTED PATH (connectionstatechange)
candidate-pair: { ... }
local-candidate: { ip: "10.0.0.2", port: 54012, protocol: "udp", candidateType: "host" }
remote-candidate: { ip: "185.123.45.67", port: 3478, protocol: "udp", candidateType: "srflx" }
[WebRTC] REAL REMOTE ENDPOINT: { ip: "185.123.45.67", port: 3478, protocol: "udp", candidateType: "srflx" }
```

If the site sends WebRTC data via `fetch`, `xhr`, `WebSocket` or `sendBeacon`, the script will show that too:

```
[NET][fetch] https://site.example/api
[NET] SDP detected
v=0
o=- 46117317 2 IN IP4 127.0.0.1
...

[NET][ws] wss://site.example/socket
[NET] ICE detected
{"candidate":"candidate:...","sdpMid":"0","sdpMLineIndex":0}
```

### What to look at first

* `\[TM] WebRTC hook installed` — the script loaded successfully.
* `\[WebRTC] created` — the page actually created a WebRTC connection.
* `\[WebRTC] local candidate parsed` — the local candidate is visible.
* `\[WebRTC] remote candidate parsed` — the remote candidate is visible.
* `\[WebRTC] REAL REMOTE ENDPOINT` — the most useful log. It shows the final remote endpoint chosen by WebRTC.

### If there are few logs

This script adds two manual commands to the console:

```javascript
__dumpAllWebRTCSelectedPaths()
__dumpAllWebRTCStats()
```

The first command reprints the selected paths.

The second shows a full snapshot of `candidate-pair`, `local-candidate`, `remote-candidate` and `transport`.

## Useful to check after installation

After starting the script, you can check WebRTC behavior using the services from the article [How to check for a WebRTC leak](https://docs.proxyshard.com/eng/our-products/about-udp/webrtc-leak-check-tools).

If you want to understand the mechanism of the leak itself, see the article [How a leak through WebRTC works](https://docs.proxyshard.com/eng/our-products/about-udp/how-webrtc-leak-works).