It's a route param - not query string. If the parameter doesn't exist it means the route is different.

[luke-hanwook]

          It's a route param - not query string. If the parameter doesn't exist it means the route is different.

Let's say you have this configuration: /group/:groupId/post/:postId
If groupId is undefined the route will be /group/post/<postId> and if postId is undefined the route will be /group/<groupId>/post
These two examples should match different routes than /group/:groupId/post/:postId

A common convention is that path/route params are manditory while query params are optional.

Originally posted by @tzachov in remix-run/react-router#8498 (comment)

[yeliex]

the component should decide it can receive optionally params actually

eg:

const Page = () => {
    const params = useParams<{ id1: string; id2?: string }>;
}

const route = [
  {
      path: '/item/:id1/item2/:id2',
      Component: Page
  }, 
  {
    path: '/item/:id1',
    Component: Page
  }
];

the case should be defined in route manually and could be known by developer