# Splits

Splits allow you to divide a line item's traffic into segments, each with its own targeting, CPM, and creatives. This is useful for A/B testing, geo-based pricing, or running different creatives for different audiences within the same campaign.

## How splits work

When a line item has splits defined, the system evaluates each split independently:

1. **Traffic allocation**: Each split has a `percentage` (0 to 1). A random number is drawn and compared. If the random value is below the percentage, the split is considered for delivery.
2. **Targeting**: The split's targeting criteria are evaluated (AND logic). All criteria must pass.
3. **Creative matching**: The split's creatives are matched against the impression (dimension matching for banners).
4. **Fallback**: If no split is eligible, the line item's own creatives are used as a fallback (subject to dimension matching).

## Split structure

| Field           | Type           | Description                                                      |
| --------------- | -------------- | ---------------------------------------------------------------- |
| `id`            | number         | Unique split identifier                                          |
| `name`          | string         | Split name                                                       |
| `percentage`    | number         | Traffic allocation ratio (0 to 1, where 0.5 = 50%)               |
| `cpm`           | number         | CPM override for this split (0 = use line item rate)             |
| `targeting`     | object         | Split-level targeting criteria                                   |
| `creatives`     | array          | Creatives specific to this split                                 |
| `goal`          | number \| null | Split-level delivery goal                                        |
| `goalType`      | string         | `impressions`, `clicks`, or `spend`                              |
| `pacingType`    | string         | `asap`, `even`, or `frontloaded`                                 |
| `deliveryRatio` | number         | Dynamic delivery ratio (0 to 1), calculated by the pacing system |

## Split targeting

Line items and splits share the **same `Targeting` shape**. See the full attribute reference in [Targeting](/campaign-delivery/targeting.md). Each attribute uses `{ excluded: boolean, value: [...] }` (or an array of `{ excluded, value: Record<string,string[]> }` for the data-targeting variants).

| Attribute              | Description                                                      |
| ---------------------- | ---------------------------------------------------------------- |
| `geography`            | Country, region, or city (mixed levels supported)                |
| `domain`               | Publisher domain (wildcard support)                              |
| `site`                 | Nexx360 site ID                                                  |
| `tagId`                | Nexx360 tag ID                                                   |
| `page`                 | Exact `site.page` URL                                            |
| `device`               | Device type                                                      |
| `os`                   | Operating system                                                 |
| `browser`              | Browser (substring match on UA)                                  |
| `browserLanguage`      | Device language (prefix matching)                                |
| `connection`           | Connection type                                                  |
| `keyword`              | Page keywords                                                    |
| `firstId`              | First-party ID from `user.ext.eids` (source `first-id.fr`)       |
| `dayandtime`           | Day of week + hour range (e.g. Monday 09:00–17:00)               |
| `viewabilityThreshold` | Minimum viewability percentage                                   |
| `impData`              | Per-impression data (`imp.ext.data`)                             |
| `siteAppData`          | Site or app data (`site.ext.data`, falls back to `app.ext.data`) |
| `userData`             | User data (`user.ext.data`)                                      |

### Day and time targeting example

Target weekdays during business hours:

```json
{
  "dayandtime": {
    "excluded": false,
    "value": [
      { "day": ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"], "hours": { "start": "09:00", "end": "17:00" } }
    ]
  }
}
```

### Data targeting example

```json
{
  "userData": [
    { "excluded": false, "value": { "audience": ["premium"] } },
    { "excluded": true,  "value": { "category": ["adult"] } }
  ]
}
```

## Split CPM

When a split has `cpm > 0`, that CPM overrides the line item's base rate for creatives delivered through that split. The split CPM is used in bid selection and appears in the bid response.

## Delivery capping per split

Each split can be independently capped. See [Pacing and Capping](/campaign-delivery/pacing-and-capping.md) for details.


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