# Source: https://nextjs.org/docs/app/api-reference/functions/generate-image-metadata.md

# generateImageMetadata
@doc-version: 16.0.4


You can use `generateImageMetadata` to generate different versions of one image or return multiple images for one route segment. This is useful for when you want to avoid hard-coding metadata values, such as for icons.

## Parameters

`generateImageMetadata` function accepts the following parameters:

#### `params` (optional)

An object containing the [dynamic route parameters](/docs/app/api-reference/file-conventions/dynamic-routes.md) object from the root segment down to the segment `generateImageMetadata` is called from.

```tsx filename="icon.tsx" switcher
export function generateImageMetadata({
  params,
}: {
  params: { slug: string }
}) {
  // ...
}
```

```jsx filename="icon.js" switcher
export function generateImageMetadata({ params }) {
  // ...
}
```

| Route                           | URL         | `params`                  |
| ------------------------------- | ----------- | ------------------------- |
| `app/shop/icon.js`              | `/shop`     | `undefined`               |
| `app/shop/[slug]/icon.js`       | `/shop/1`   | `{ slug: '1' }`           |
| `app/shop/[tag]/[item]/icon.js` | `/shop/1/2` | `{ tag: '1', item: '2' }` |

## Returns

The `generateImageMetadata` function should return an `array` of objects containing the image's metadata such as `alt` and `size`. In addition, each item **must** include an `id` value which will be passed as a promise to the props of the image generating function.

| Image Metadata Object | Type                                |
| --------------------- | ----------------------------------- |
| `id`                  | `string` (required)                 |
| `alt`                 | `string`                            |
| `size`                | `{ width: number; height: number }` |
| `contentType`         | `string`                            |

```tsx filename="icon.tsx" switcher
import { ImageResponse } from 'next/og'

export function generateImageMetadata() {
  return [
    {
      contentType: 'image/png',
      size: { width: 48, height: 48 },
      id: 'small',
    },
    {
      contentType: 'image/png',
      size: { width: 72, height: 72 },
      id: 'medium',
    },
  ]
}

export default async function Icon({ id }: { id: Promise<string | number> }) {
  const iconId = await id
  return new ImageResponse(
    (
      <div
        style={{
          width: '100%',
          height: '100%',
          display: 'flex',
          alignItems: 'center',
          justifyContent: 'center',
          fontSize: 88,
          background: '#000',
          color: '#fafafa',
        }}
      >
        Icon {iconId}
      </div>
    )
  )
}
```

```jsx filename="icon.js" switcher
import { ImageResponse } from 'next/og'

export function generateImageMetadata() {
  return [
    {
      contentType: 'image/png',
      size: { width: 48, height: 48 },
      id: 'small',
    },
    {
      contentType: 'image/png',
      size: { width: 72, height: 72 },
      id: 'medium',
    },
  ]
}

export default async function Icon({ id }) {
  const iconId = await id
  return new ImageResponse(
    (
      <div
        style={{
          width: '100%',
          height: '100%',
          display: 'flex',
          alignItems: 'center',
          justifyContent: 'center',
          fontSize: 88,
          background: '#000',
          color: '#fafafa',
        }}
      >
        Icon {iconId}
      </div>
    )
  )
}
```

## Image generation function props

When using `generateImageMetadata`, the default export image generation function receives the following props:

#### `id`

A promise that resolves to the `id` value from one of the items returned by `generateImageMetadata`. The `id` will be a `string` or `number` depending on what was returned from `generateImageMetadata`.

```tsx filename="icon.tsx" switcher
export default async function Icon({ id }: { id: Promise<string | number> }) {
  const iconId = await id
  // Use iconId to generate the image
}
```

```jsx filename="icon.js" switcher
export default async function Icon({ id }) {
  const iconId = await id
  // Use iconId to generate the image
}
```

#### `params` (optional)

A promise that resolves to an object containing the [dynamic route parameters](/docs/app/api-reference/file-conventions/dynamic-routes.md) from the root segment down to the segment the image is colocated in.

```tsx filename="icon.tsx" switcher
export default async function Icon({
  params,
}: {
  params: Promise<{ slug: string }>
}) {
  const { slug } = await params
  // Use slug to generate the image
}
```

```jsx filename="icon.js" switcher
export default async function Icon({ params }) {
  const { slug } = await params
  // Use slug to generate the image
}
```

### Examples

#### Using external data

This example uses the `params` object and external data to generate multiple [Open Graph images](/docs/app/api-reference/file-conventions/metadata/opengraph-image.md) for a route segment.

```tsx filename="app/products/[id]/opengraph-image.tsx" switcher
import { ImageResponse } from 'next/og'
import { getCaptionForImage, getOGImages } from '@/app/utils/images'

export async function generateImageMetadata({
  params,
}: {
  params: { id: string }
}) {
  const images = await getOGImages(params.id)

  return images.map((image, idx) => ({
    id: idx,
    size: { width: 1200, height: 600 },
    alt: image.text,
    contentType: 'image/png',
  }))
}

export default async function Image({
  params,
  id,
}: {
  params: Promise<{ id: string }>
  id: Promise<number>
}) {
  const productId = (await params).id
  const imageId = await id
  const text = await getCaptionForImage(productId, imageId)

  return new ImageResponse(
    (
      <div
        style={
          {
            // ...
          }
        }
      >
        {text}
      </div>
    )
  )
}
```

```jsx filename="app/products/[id]/opengraph-image.js" switcher
import { ImageResponse } from 'next/og'
import { getCaptionForImage, getOGImages } from '@/app/utils/images'

export async function generateImageMetadata({ params }) {
  const images = await getOGImages(params.id)

  return images.map((image, idx) => ({
    id: idx,
    size: { width: 1200, height: 600 },
    alt: image.text,
    contentType: 'image/png',
  }))
}

export default async function Image({ params, id }) {
  const productId = (await params).id
  const imageId = await id
  const text = await getCaptionForImage(productId, imageId)

  return new ImageResponse(
    (
      <div
        style={
          {
            // ...
          }
        }
      >
        {text}
      </div>
    )
  )
}
```

## Version History

| Version   | Changes                                                                                             |
| --------- | --------------------------------------------------------------------------------------------------- |
| `v16.0.0` | `id` passed to the Image generation function is now a promise that resolves to `string` or `number` |
| `v16.0.0` | `params` passed to the Image generation function is now a promise that resolves to an object        |
| `v13.3.0` | `generateImageMetadata` introduced.                                                                 |
## Next Steps

View all the Metadata API options.

- [Metadata Files](/docs/app/api-reference/file-conventions/metadata.md)
  - API documentation for the metadata file conventions.