router-core/path-params

Path params capture dynamic URL segments into named variables. They are defined with a $ prefix in the route path.

CRITICAL: Never interpolate params into the to string. Always use the params prop. This is the most common agent mistake for path params.

CRITICAL: Types are fully inferred. Never annotate the return of useParams().

Dynamic Segments

A segment prefixed with $ captures text until the next /.

// src/routes/posts.$postId.tsx
import { createFileRoute } from "@tanstack/react-router"

export const Route = createFileRoute("/posts/$postId")({
  loader: async ({ params }) => {
    // params.postId is string — fully inferred, do not annotate
    return fetchPost(params.postId)
  },
  component: PostComponent,
})

function PostComponent() {
  const { postId } = Route.useParams()
  const data = Route.useLoaderData()
  return (
    <h1>
      Post {postId}: {data.title}
    </h1>
  )
}

Multiple dynamic segments work across path levels:

// src/routes/teams.$teamId.members.$memberId.tsx
export const Route = createFileRoute("/teams/$teamId/members/$memberId")({
  component: MemberComponent,
})

function MemberComponent() {
  const { teamId, memberId } = Route.useParams()
  return (
    <div>
      Team {teamId}, Member {memberId}
    </div>
  )
}

Splat / Catch-All Routes

A route with a path ending in $ (bare dollar sign) captures everything after it. The value is available under the _splat key.

// src/routes/files.$.tsx
import { createFileRoute } from "@tanstack/react-router"

export const Route = createFileRoute("/files/$")({
  component: FileViewer,
})

function FileViewer() {
  const { _splat } = Route.useParams()
  // URL: /files/documents/report.pdf → _splat = "documents/report.pdf"
  return <div>File path: {_splat}</div>
}

Optional Params

Optional params use {-$paramName} syntax. The segment may or may not be present. When absent, the value is undefined.

// src/routes/posts.{-$category}.tsx
import { createFileRoute } from "@tanstack/react-router"

export const Route = createFileRoute("/posts/{-$category}")({
  component: PostsComponent,
})

function PostsComponent() {
  const { category } = Route.useParams()
  // URL: /posts → category is undefined
  // URL: /posts/tech → category is "tech"
  return <div>{category ? `Posts in ${category}` : "All Posts"}</div>
}

Multiple optional params:

// Matches: /posts, /posts/tech, /posts/tech/hello-world
export const Route = createFileRoute("/posts/{-$category}/{-$slug}")({
  component: PostComponent,
})

i18n with Optional Locale

// src/routes/{-$locale}/about.tsx
import { createFileRoute } from "@tanstack/react-router"

export const Route = createFileRoute("/{-$locale}/about")({
  component: AboutComponent,
})

function AboutComponent() {
  const { locale } = Route.useParams()
  const currentLocale = locale || "en"
  return <h1>{currentLocale === "fr" ? "À Propos" : "About Us"}</h1>
}
// Matches: /about, /en/about, /fr/about

Prefix and Suffix Patterns

Curly braces {} around $paramName allow text before or after the dynamic part within a single segment.

Prefix

// src/routes/posts/post-{$postId}.tsx
import { createFileRoute } from "@tanstack/react-router"

export const Route = createFileRoute("/posts/post-{$postId}")({
  component: PostComponent,
})

function PostComponent() {
  const { postId } = Route.useParams()
  // URL: /posts/post-123 → postId = "123"
  return <div>Post ID: {postId}</div>
}

Suffix

// src/routes/files/{$fileName}[.]txt.tsx
import { createFileRoute } from "@tanstack/react-router"

export const Route = createFileRoute("/files/{$fileName}.txt")({
  component: FileComponent,
})

function FileComponent() {
  const { fileName } = Route.useParams()
  // URL: /files/readme.txt → fileName = "readme"
  return <div>File: {fileName}.txt</div>
}

Combined Prefix + Suffix

// URL: /users/user-456.json → userId = "456"
export const Route = createFileRoute("/users/user-{$userId}.json")({
  component: UserComponent,
})

function UserComponent() {
  const { userId } = Route.useParams()
  return <div>User: {userId}</div>
}

Navigating with Path Params

Object Form

import { Link } from "@tanstack/react-router"

function PostLink({ postId }: { postId: string }) {
  return (
    <Link to="/posts/$postId" params={{ postId }}>
      View Post
    </Link>
  )
}

Function Form (Preserves Other Params)

function PostLink({ postId }: { postId: string }) {
  return (
    <Link to="/posts/$postId" params={(prev) => ({ ...prev, postId })}>
      View Post
    </Link>
  )
}

Programmatic Navigation

import { useNavigate } from "@tanstack/react-router"

function GoToPost({ postId }: { postId: string }) {
  const navigate = useNavigate()

  return (
    <button
      onClick={() => {
        navigate({ to: "/posts/$postId", params: { postId } })
      }}
    >
      Go to Post
    </button>
  )
}

Navigating with Optional Params

// Include the optional param
<Link to="/posts/{-$category}" params={{ category: 'tech' }}>
  Tech Posts
</Link>

// Omit the optional param (renders /posts)
<Link to="/posts/{-$category}" params={{ category: undefined }}>
  All Posts
</Link>

Reading Params Outside Route Components

useParams with from

import { useParams } from "@tanstack/react-router"

function PostHeader() {
  const { postId } = useParams({ from: "/posts/$postId" })
  return <h2>Post {postId}</h2>
}

useParams with strict: false

function GenericBreadcrumb() {
  const params = useParams({ strict: false })
  // params is a union of all possible route params
  return <span>{params.postId ?? "Home"}</span>
}

Params in Loaders and beforeLoad

export const Route = createFileRoute("/posts/$postId")({
  beforeLoad: async ({ params }) => {
    // params.postId available here
    const canView = await checkPermission(params.postId)
    if (!canView) throw redirect({ to: "/unauthorized" })
  },
  loader: async ({ params }) => {
    return fetchPost(params.postId)
  },
})

Allowed Characters

By default, params are encoded with encodeURIComponent. Allow extra characters via router config:

import { createRouter } from "@tanstack/react-router"

const router = createRouter({
  routeTree,
  pathParamsAllowedCharacters: ["@", "+"],
})

Allowed characters: ;, :, @, &, =, +, $, ,.

Common Mistakes

1. CRITICAL (cross-skill): Interpolating path params into to string

// WRONG — breaks type safety and param encoding
<Link to={`/posts/${postId}`}>Post</Link>

// CORRECT — use params prop
<Link to="/posts/$postId" params={{ postId }}>Post</Link>

2. MEDIUM: Using * for splat routes instead of $

TanStack Router uses $ for splat routes. The captured value is under _splat, not *.

// WRONG (React Router / other frameworks)
// <Route path="/files/*" />

// CORRECT (TanStack Router)
// File: src/routes/files.$.tsx
export const Route = createFileRoute("/files/$")({
  component: () => {
    const { _splat } = Route.useParams()
    return <div>{_splat}</div>
  },
})

Note: * works in v1 for backwards compatibility but will be removed in v2. Always use _splat.

3. MEDIUM: Using curly braces for basic dynamic segments

Curly braces are ONLY for prefix/suffix patterns and optional params. Basic dynamic segments use bare $.

// WRONG — braces not needed for basic params
createFileRoute("/posts/{$postId}")

// CORRECT — bare $ for basic dynamic segments
createFileRoute("/posts/$postId")

// CORRECT — braces for prefix pattern
createFileRoute("/posts/post-{$postId}")

// CORRECT — braces for optional param
createFileRoute("/posts/{-$category}")

4. Params are always strings

Path params are always parsed as strings. If you need a number, parse in the loader or component:

export const Route = createFileRoute("/posts/$postId")({
  loader: async ({ params }) => {
    const id = parseInt(params.postId, 10)
    if (isNaN(id)) throw notFound()
    return fetchPost(id)
  },
})

You can also use params.parse and params.stringify on the route for bidirectional transformation:

export const Route = createFileRoute("/posts/$postId")({
  params: {
    parse: (raw) => ({ postId: parseInt(raw.postId, 10) }),
    stringify: (parsed) => ({ postId: String(parsed.postId) }),
  },
  loader: async ({ params }) => {
    // params.postId is now number
    return fetchPost(params.postId)
  },
})