# Creative Selection

After a line item passes eligibility checks, its creatives are filtered based on the impression type and dimensions.

## Banner creative matching

For banner impressions, each creative's width and height must match the impression:

* If `imp.banner.format` is defined, the creative dimensions must match one of the format entries
* Otherwise, the creative must match `imp.banner.w` and `imp.banner.h`

Only creatives with matching dimensions are eligible.

## Native creative matching

For native impressions, the creative's `content` field must be a JSON object with fields that satisfy the **required** assets in the bid request's `imp.native.request`.

The creative content uses a simplified JSON format:

```json
{
  "title": "Ad Title",
  "img": "https://cdn.example.com/main.jpg",
  "icon": "https://cdn.example.com/icon.png",
  "description": "Ad description text",
  "brand": "Advertiser Name",
  "cta": "Learn More",
  "price": "$9.99",
  "clickUrl": "https://advertiser.com/landing"
}
```

Each field maps to an OpenRTB Native 1.2 asset type:

| Creative field | Native asset type           | OpenRTB type ID |
| -------------- | --------------------------- | --------------- |
| `title`        | Title                       | title           |
| `img`          | Main image                  | img type 3      |
| `icon`         | Icon image                  | img type 1      |
| `brand`        | Sponsored (advertiser name) | data type 1     |
| `description`  | Description                 | data type 2     |
| `cta`          | Call to action text         | data type 12    |
| `price`        | Price                       | data type 6     |
| `clickUrl`     | Click-through URL           | link.url        |

**Eligibility:** A creative is eligible if it has content for all assets marked as `required: 1` in the bid request. Optional assets (`required: 0`) do not affect eligibility.

**Response building:** The DSP builds a Native 1.2 response using only the assets present in the bid request and maps each response asset ID to match the corresponding request asset ID (required by Prebid.js).

## Video and audio

For video and audio impressions, all creatives of the line item are eligible regardless of dimensions.

## Creative fields

| Field        | Type                | Description                                                       |
| ------------ | ------------------- | ----------------------------------------------------------------- |
| `id`         | number              | Unique creative identifier                                        |
| `name`       | string              | Creative name                                                     |
| `status`     | string              | `active` or `paused`                                              |
| `isArchived` | boolean             | Whether the creative is archived                                  |
| `w`          | number \| undefined | Width in pixels (required for banner, optional otherwise)         |
| `h`          | number \| undefined | Height in pixels (required for banner, optional otherwise)        |
| `adomain`    | string              | Advertiser domain (e.g. `advertiser.com`)                         |
| `content`    | string              | Ad markup (HTML for banners, VAST XML for video, JSON for native) |
| `mediatype`  | string              | `banner`, `video`, `native`, or `audio`                           |
| `weight`     | number              | Weight for creative rotation (default: 1)                         |

## Creative rotation

When multiple creatives from the same line item match an impression, they are all included as candidates. The final selection is based on bid price (see [Bid Selection](/campaign-delivery/bid-selection.md)).

## Split creatives

When a line item uses splits, each split can have its own set of creatives. If a split is eligible, only that split's creatives are used (subject to the same dimension matching rules). If no split is eligible, the line item's base creatives are used as a fallback.


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