preferredRegion

The preferredRegion option allows you to specify the preferred deployment region for a route segment. This value is passed to your deployment platform.

export const preferredRegion = // string || string[]

• string: Deploy the route to a specific region. Available region codes are platform-specific. For example, 'iad1'.
• string[]: Deploy the route to multiple specific regions. The route is deployed to all listed regions, not a single one chosen from the list. For example, ['iad1', 'sfo1'].

Good to know:

• If a preferredRegion is not specified, it will inherit the option of the nearest parent layout. The root layout defaults to 'auto'.
• A child segment's value overrides the parent, values are not merged.
• Next.js passes the region values through to the deployment platform. The exact behavior and available region codes are platform-specific. Refer to your deployment platform's documentation for supported values.

Vercel

If deploying Next.js on Vercel, regions are only supported if export const runtime = 'edge' is set. The following options can be passed:

• 'auto' (default): Uses the default region.
• 'global': Prefer deploying the route to all availableregions.
• 'home': Prefer deploying the route to the home region.

If an unsupported value is passed, an error will be thrown.