> For the complete documentation index, see [llms.txt](https://developers.usetoggle.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.usetoggle.com/key-concepts/overview/card-numbers.md).

# Card number formats

### Issuer Identification Number (IIN)

Toggle card unique codes are all 19 digits long. This includes an 8 digit IIN prefix of `63011900`. This is a unique, globally recognised identifier of Toggle cards. You'll see us refer to the full card unique code as a `card_reference`.

{% hint style="info" %}
**Card number example**

`6301190060337576946`
{% endhint %}

### Card aliases

Toggle can also ingest cards from other providers. In such cases, the ingested cards will have both a Toggle `card_reference` but also a `card_alias.`

If you are handling cards with both a `card_reference` and a `card_alias`,  it is good practice to use the **alias** in all communication with the card holder, as the card holder will likely only have a copy of the card\_alias, whereas the Toggle `card_reference` is essentially masked from public view.