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

# Surfaces

A **surface** is a location in your application where treatments can appear. Surfaces define the "where" of treatment delivery — the specific screen, page, or touchpoint a user is on when they receive a treatment.

***

## Surface Identification and API Usage

Immediately below is an example of how the surface field is used in a [Get Treatments API](/api-reference/get-treatments) request. Each surface is identified by a name written in `SCREAMING_SNAKE_CASE` (for example, `HOME_SCREEN`). Every [Treatment Type](/concepts/treatment-types) defines the surfaces where it can be applied. When your app requests a treatment, it includes the surface identifier, which Auxia uses to determine which treatments are eligible.

```json theme={null}
{
    "userId": "USER_ID",
    "surfaces": [
        {
            "surface": "HOME_SCREEN",
            "maximumTreatmentCount": 1
        }
    ]
    // ... additional fields — see the Get Treatments API reference for the full request structure
}
```

***

## Configuration

Surfaces are created and managed in **Configuration > UI Layout > Surfaces**. This requires admin permissions. Contact your admin to add new surfaces or modify existing ones.

***

## Examples

| Surface Name          | Typical Use                                         |
| --------------------- | --------------------------------------------------- |
| `HOME_SCREEN`         | Welcome messages, featured promotions               |
| `PRODUCT_DETAIL_PAGE` | Upsell, related items, personalized recommendations |
| `CHECKOUT_PAGE`       | Discount offers, cart recovery prompts              |
| `SEARCH_RESULTS`      | Sponsored or personalized result callouts           |
| `SETTINGS`            | Upgrade prompts, feature discovery                  |

***

## Related Concepts

* [Treatments](/concepts/treatments) — treatments are assigned to a surface
* [Treatment Types](/concepts/treatment-types) — treatment types define which surfaces they can appear on
* [Destinations](/concepts/destinations) — destinations handle delivery for out-of-product channels

**How-to guides:** [Configuration](/guides/comprehensive/configuration)