# Lifecycle hooks

> Call an action when your Snap is installed or updated.

# Lifecycle hooks

You can implement lifecycle hooks to automatically run an action, such as displaying a dialog or
notification, when a user installs or updates your Snap.

## Steps

### 1. Request permission to implement lifecycle hooks

Request the [`endowment:lifecycle-hooks`](../reference/permissions.md#endowmentlifecycle-hooks)
permission.
Add the following to your Snap's manifest file:

```json title="snap.manifest.json"
"initialPermissions": {
  "endowment:lifecycle-hooks": {}
}
```

### 2. Run an action on installation

To run an action when a user installs your Snap, expose the
[`onInstall`](../reference/entry-points.md#oninstall) entry point and implement the action.
For example, you can use `onInstall` to perform any initialization that is required upon installation.

The following example displays an [alert dialog](custom-ui/dialogs.md#display-an-alert-dialog) upon installation:

<Tabs>

<TabItem value="JSX">

```tsx title="index.tsx"

export const onInstall: OnInstallHandler = async () => {
  await snap.request({
    method: 'snap_dialog',
    params: {
      type: 'alert',
      content: (
        <Box>
          <Heading>Installation successful</Heading>
          <Text>
            To use this Snap, visit the companion dapp at{' '}
            metamask.io.
          </Text>
        </Box>
      ),
    },
  })
}
```

</TabItem>
<TabItem value="Functions" deprecated>

```typescript title="index.ts"

export const onInstall: OnInstallHandler = async () => {
  await snap.request({
    method: 'snap_dialog',
    params: {
      type: 'alert',
      content: panel([
        heading('Installation successful'),
        text('To use this Snap, visit the companion dapp at [metamask.io](https://metamask.io).'),
      ]),
    },
  })
}
```

</TabItem>
</Tabs>

### 3. Run an action on update

To run an action when a user updates your Snap, expose the
[`onUpdate`](../reference/entry-points.md#onupdate) entry point and implement the action.
For example, you can use `onUpdate` to perform any migrations that are required upon update.

The following example displays an [alert dialog](custom-ui/dialogs.md#display-an-alert-dialog) upon update:

<Tabs>

<TabItem value="JSX">

```tsx title="index.tsx"

export const onUpdate: OnUpdateHandler = async () => {
  await snap.request({
    method: 'snap_dialog',
    params: {
      type: 'alert',
      content: (
        <Box>
          <Heading>Update successful</Heading>
          <Text>New features added in this version:</Text>
          <Text>Added a dialog that appears when updating.</Text>
        </Box>
      ),
    },
  })
}
```

</TabItem>
<TabItem value="Functions" deprecated>

```typescript title="index.ts"

export const onUpdate: OnUpdateHandler = async () => {
  await snap.request({
    method: 'snap_dialog',
    params: {
      type: 'alert',
      content: panel([
        heading('Update successful'),
        text('New features added in this version:'),
        text('Added a dialog that appears when updating.'),
      ]),
    },
  })
}
```

</TabItem>
</Tabs>

## Example

See the [`@metamask/lifecycle-hooks-example-snap`](https://github.com/MetaMask/snaps/tree/main/packages/examples/packages/lifecycle-hooks)
package for a full example of implementing lifecycle hooks.