# Load the JavaScript tag through your own domain

Load the JavaScript tag and send its data through a subdomain you own, like `t.example.com`, instead of Better Stack's hosts. Use it when your pages may only talk to your own domain, and to keep the tag working for visitors with ad blockers.

## Add your subdomain

1. Go to **Error tracking** → [Applications](https://errors.betterstack.com/team/0/applications/ ";_blank")
2. Next to your application, click **⋯** → **Configure**.
3. Open the **Frontend** tab.
4. At the bottom of the page, click **Advanced settings**.
5. Under **Your own domain**, enter a subdomain of a domain you own, like `t.example.com`. Avoid words ad blockers look for, such as `analytics`, `tracking` or `telemetry`.
6. Click **Save changes**.

## Add the CNAME record

At your DNS provider, add a CNAME record for your subdomain:

| Type | Name | Target |
|---|---|---|
| CNAME | `t` | `proxy.betterstack.net` |

In Cloudflare, set the record to **DNS only**, so Cloudflare doesn't proxy it.

Better Stack checks the record, usually in under a minute. Once it's right, the **Subdomain** field shows a green check with the tooltip **CNAME configured correctly**.

## Update the snippet

1. Reload the **Frontend** page.
2. Copy the snippet at the top. It now loads the tag from your subdomain.
3. Replace the snippet on your pages with it.

The tag now sends errors, session replays, web events and console logs through your subdomain.

[warning]
#### Removing your subdomain later?
First switch your pages back to a snippet that loads the tag from `betterstack.net`. Pages that load it from your subdomain stop collecting data once the subdomain or its CNAME record is removed.
[/warning]

## Use your own reverse proxy

Already run a reverse proxy on your domain, like a Cloudflare Worker or nginx? Point the tag at it instead of adding the CNAME record, and leave **Subdomain** in Better Stack empty. Your proxy needs to:

- Forward `/b.js` to `https://betterstack.net/b.js`, keeping the query string.
- Forward every other path, with its query string, to the host named in its first segment. For example, `https://t.example.com/s123.eu-nbg-2.betterstackdata.com/web/123` goes to `https://s123.eu-nbg-2.betterstackdata.com/web/123`. Only forward to `betterstack.net` and `*.betterstackdata.com`.
- Put the visitor's IP address first in `X-Forwarded-For`. Otherwise, Better Stack shows your proxy's address and location instead of the visitor's.

Then load the tag from your proxy, and set `proxyHost` before `init`:

```html
[label Load the tag through your reverse proxy]
<script>
  !function(b,e,t,r){
    b[t]=b[t]||function(...args){(b[t].q=b[t].q||[]).push(args)};
    b[t].l=+new Date;
    var s=e.createElement('script'); s.async=1; s.crossOrigin='anonymous';
    [highlight]
    s.src='https://t.example.com/b.js?t='+r;
    [/highlight]
    (e.head||e.getElementsByTagName('head')[0]).appendChild(s);
  }(window,document,'betterstack','$APPLICATION_TOKEN');
  [highlight]
  betterstack('config', { proxyHost: 'https://t.example.com' });
  [/highlight]
  betterstack('init', { environment: 'production' });
</script>
```

## Bundle the tag with your app

Some environments, like a Twitch extension, only run scripts bundled with your app.

1. Download the tag:

    ```bash
    [label Download the JavaScript tag]
    curl -o betterstack.js "https://betterstack.net/b.js?t=$APPLICATION_TOKEN"
    ```

2. Load `betterstack.js` in your build in place of the snippet.
3. After it runs, start the tag through your subdomain or reverse proxy:

    ```javascript
    [label Start the bundled tag]
    betterstack('config', { proxyHost: 'https://t.example.com' });
    betterstack('init', { environment: 'production' });
    ```

The copy keeps the settings it was downloaded with, so download it again after you change them in Better Stack.

## Next steps

- [Installation](https://betterstack.com/docs/errors/js-tag/install/): snippet, init options, identifying users, tracking custom events.
- [Configuration](https://betterstack.com/docs/errors/js-tag/configure/): UI settings, collection toggles, sampling, session replays, sessions, batching, and more.