# Tunneling

If you are developing on your local computer with one of the following integrations:

- Office Scripts
- Google Apps Script

you will need to expose your development server via a tunneling solution. This is because Office Scripts and Google Apps Script can only connect to servers on the Internet, but not directly to your local computer.

Note that tunneling is never required if you use an online development environment such as [GitHub Codespaces](../github_codespaces/index.md).

#### NOTE
It’s important to trust the tunneling provider, as you are granting them access to route traffic to and from your local machine. Always ensure you are using a reputable provider to maintain the security of your development environment and check with your IT security department for allowed providers.

## ngrok

[ngrok](https://ngrok.com/) is a popular provider and free for what we’ll use it for. Start by following their official docs:

1. [Create an account](https://dashboard.ngrok.com/signup)
2. [Install ngrok](https://ngrok.com/download)

Now you can run the following command on your Terminal/Command Prompt:

```text
ngrok http 8000
```

You should see something along the following lines:

```text
ngrok                                                                                                                (Ctrl+C to quit)

Share what you're building with ngrok https://ngrok.com/share-your-ngrok-story

Session Status                online
Account                       xxx@xxx.com (Plan: Free)
Version                       3.16.0
Region                        Europe (eu)
Web Interface                 http://127.0.0.1:4040
Forwarding                    https://xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx.ngrok-free.app -> http://localhost:8000

Connections                   ttl     opn     rt1     rt5     p50     p90
                            0       0       0.00    0.00    0.00    0.00
```

`https://xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx.ngrok-free.app` is the URL that you need to use as base URL in your `runPython` function in Office Scripts and Google Apps Script. This means that the complete URL to call a custom script would be (make sure to replace `hello_world` with the name of your custom script):

```default
https://xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx.ngrok-free.app/xlwings/custom-scripts-call/hello_world
```

To exit ngrok again, hit `Ctrl-C` in your Terminal/Command Prompt.

#### NOTE
- If you have certificates in your `certs` folder (see [Development Certificates](../dev_certificates/index.md)), you will need to run ngrok as follows so it connects to your local server running on https:
  ```text
  ngrok http https://127.0.0.1:8000
  ```
- You can configure ngrok so that it will always use the same URL, see the [docs](https://ngrok.com/docs/getting-started/#step-4-always-use-the-same-domain).
- Note that by default, ngrok will expose your local web server publicly so anyone with the URL can access your backend.

## Alternatives

Instead of ngrok, you can use many other solutions such as [Cloudflare Tunnel](https://developers.cloudflare.com/cloudflare-one/connections/connect-networks/). For a curated list of alternatives, see [Awesome Tunneling](https://github.com/anderspitman/awesome-tunneling).