The dynamicParams option allows you to control what happens when a dynamic segment is visited that was not generated with generateStaticParams.

export const dynamicParams = true // true | false

export const dynamicParams = true // true | false

• true (default): Dynamic route segments not included in generateStaticParams are generated at request time.
• false: Dynamic route segments not included in generateStaticParams will return a 404.

Good to know:

• This option replaces the fallback: true | false | blocking option of getStaticPaths in the pages directory.
• dynamicParams is not available when Cache Components is enabled.

Source: docs/01-app/03-api-reference/03-file-conventions/02-route-segment-config/dynamicParams.mdx