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

# Native Multi-Media

> Learn how to place up to three image or video areas (media) in a single native Ad Unit and receive a file sized for each media item from advertisers.

## What is Multi-Media?

A native Ad Unit has one image or video area by default. This area is called **media**. With **Add Media**, a unit can have up to three media items: advertisers register one creative with a file sized for each media item, and your app tells the media items apart by **ID** and places each one wherever you want.

Use it when a single ad needs images or videos of different sizes. For example, you can place a landscape main image and a square thumbnail together in one ad.

***

## Prerequisites

* The unit format must be **Native**, with a size other than **No Image/Video** selected in **Media Size**.
* To add media to an existing unit, the unit must not have received ad requests and must not belong to an Ad Product.
* The unit must not be connected to Backfill Ads. Native units with two or more media items don't support Backfill Ads, so use a native unit with a single media item for placements that need Backfill Ads.

***

## Add Media

<Steps>
  <Step title="Select Native Format">
    On the Ad Unit creation screen, select **Native** as the unit format, then select the size of the first media item in **Media Size**.
  </Step>

  <Step title="Add Media">
    Click **Add Media**. Click it again if you need another media item (up to three).
  </Step>

  <Step title="Enter Media Details">
    Enter a **Label** and **Size** for each media item, and change the **ID** of Media 2 and 3 if needed. See [Media Fields](#media-fields) for each field.
  </Step>

  <Step title="Save Unit">
    When you finish, save the unit.
  </Step>
</Steps>

***

## Media Fields

| Field | Description |
| - | - |
| **Label** | The media name advertisers see when they register creatives. Enter a name that describes its purpose, and decide on it before you create an Ad Product. (e.g., `Main image`, `Thumbnail`) |
| **Size** | The size of the media area in dp. Advertisers upload images at 3× the pixel resolution of this size. |
| **ID** | The value your app uses to tell media items apart. Media 1's ID is fixed to `m1`, and added media items get IDs such as `m2` and `m3` automatically. |

All three fields are required.

### ID Rules

* Use only lowercase letters, numbers, and `_`.
* An ID can't be the same as the ID of another media item or a [native additional field](/ad-unit/formats#native-additional-fields).
* `headline` and `body` are reserved for the default fields, so you can't use them.
* After you save the unit, you can't change its IDs.

<Warning>
  Your app finds media items by ID. Finalize the IDs before you start developing the app.
</Warning>

Saved IDs appear in **Media Size** on the Ad Unit detail screen. Click an ID to copy it.

***

## Edit and Delete Media

| Situation | Behavior |
| - | - |
| **Reduced to one media item** | Only the size of the remaining media item is kept, and its label and ID are cleared. The unit becomes a regular native unit with a single media item. |
| **Editing a saved multi-media unit** | You can't delete Media 1; you can delete only Media 2 and 3. |
| **Units that have received ad requests or belong to an Ad Product** | You can't change media sizes or add or delete media. |

***

## Ad Products and Creative Sets

When you create an Ad Product, multi-media units are grouped into one [Creative Set](/ad-product/create#step-2-configure-creative-sets) only if, in addition to the other set criteria, every media item has the same size and ID.

***

## Creative Registration by Advertisers

Advertisers register one creative with a file for each media item and can submit only after every media item has a file. For detailed steps, see [Registering Creatives](/campaign/creative#multi-media-creatives).

***

## Next Steps

<Card title="Creating Ad Units" icon="square-plus" href="/ad-unit/create">
  Create your own Ad Unit.
</Card>


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