useParams

Returns an object of key/value pairs of the dynamic params from the current URL that were matched by the routes. Child routes inherit all params from their parent routes.

import { useParams } from "@remix-run/react";

function SomeComponent() {
  const params = useParams();
  // ...
}

Assuming a route like routes/posts/$postId.tsx is matched by /posts/123 then params.postId will be "123".