> ## Documentation Index
> Fetch the complete documentation index at: https://www.alttextlab.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Allowed sources

> Control which image sources the web snippet will process.

By default, the web snippet processes images from any domain found on your page. You can restrict this to prevent generating alt text for external or third-party images you don't control.

Configure allowed sources in the [Web Snippets dashboard](https://app.alttextlab.com/web-snippets) under your snippet settings.

## Options

### Site domain & subdomains only

When enabled, only images hosted on your site's domain and its subdomains are processed. All other sources are ignored.

For example, if your site is `example.com`, the following images would be processed:

* `https://example.com/images/photo.jpg`
* `https://cdn.example.com/images/photo.jpg`

And the following would be ignored:

* `https://third-party-cdn.com/image.png`
* `https://google.com/test/img.png`

### Whitelist of sources (URL prefixes)

When you need images from specific external sources in addition to your own domain, add their URL prefixes to the whitelist. Any image URL that starts with a whitelisted prefix will be processed.

For example, with `https://third-party-cdn.com/images` in the whitelist, the following would be processed:

* `https://example.com/photo.jpg` *(own domain)*
* `https://cdn.example.com/photo.jpg` *(own subdomain)*
* `https://third-party-cdn.com/images/product.png` *(matches whitelist prefix)*

And the following would be ignored:

* `https://third-party-cdn.com/other/image.png` *(does not match prefix)*
* `https://google.com/test/img.png` *(not in whitelist)*

<Tip>
  We recommend enabling **Site domain & subdomains only** or maintaining an explicit whitelist rather than leaving sources unrestricted. This prevents unnecessary credit usage on external images you don't control.
</Tip>