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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/remix-run/react-router/llms.txt

Use this file to discover all available pages before exploring further.

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Type Generation

React Router Framework Mode automatically generates TypeScript types from your route configuration, providing type safety for route parameters, loader data, and more.

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Overview

The type generation system:
  • Generates types from your routes.ts configuration
  • Creates route-specific types for params, loader data, and actions
  • Updates automatically during development
  • Provides IDE autocomplete for route paths and params

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Setup

Type generation is enabled automatically when you use the Vite plugin: 
// vite.config.ts
import { reactRouter } from "@react-router/dev/vite";
import { defineConfig } from "vite";

export default defineConfig({
  plugins: [reactRouter()],
});

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Generated Files

Types are generated in .react-router/types/: 
.react-router/
└── types/
    ├── react-router-config.d.ts  # Future flags config
    ├── +server.d.ts              # Server build types
    └── app/                      # Route module types
        ├── root.d.ts
        ├── routes/
        │   ├── _index.d.ts
        │   └── posts.$id.d.ts
        └── ...
Important: Do not edit these files directly. They are regenerated automatically.

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Add to .gitignore

Add the generated types directory to .gitignore: 
.react-router/

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TypeScript Configuration

Update your tsconfig.json to include generated types: 
{
  "include": [
    "**/*.ts",
    "**/*.tsx",
    ".react-router/types/**/*"
  ],
  "compilerOptions": {
    "rootDirs": [".", "./.react-router/types"]
  }
}

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Route Module Types

Each route module gets generated type annotations: 
// app/routes/posts.$id.tsx
import type { Route } from "./+types/posts.$id";

export async function loader({ params }: Route.LoaderArgs) {
  // params.id is typed as string
  const post = await getPost(params.id);
  return { post };
}

export default function Post({ loaderData }: Route.ComponentProps) {
  // loaderData.post is typed from loader return value
  return <article>{loaderData.post.title}</article>;
}

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Available Types

Each route module exports these types:

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Route.LoaderArgs

Arguments passed to the loader function: 
export async function loader({ params, request, context }: Route.LoaderArgs) {
  // params: typed route parameters
  // request: Request object
  // context: server context
}

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Route.ActionArgs

Arguments passed to the action function: 
export async function action({ params, request, context }: Route.ActionArgs) {
  const formData = await request.formData();
  // ...
}

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Route.ComponentProps

Props for the default route component: 
export default function Component({ loaderData, actionData }: Route.ComponentProps) {
  // loaderData: typed return value from loader
  // actionData: typed return value from action
}

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Route.ErrorBoundaryProps

Props for the ErrorBoundary component: 
export function ErrorBoundary({ error }: Route.ErrorBoundaryProps) {
  // error: unknown
  return <div>Error: {String(error)}</div>;
}

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Route.HydrateFallbackProps

Props for the HydrateFallback component: 
export function HydrateFallback(props: Route.HydrateFallbackProps) {
  return <div>Loading...</div>;
}

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Route.MiddlewareArgs

Arguments for middleware functions (with future.v8_middleware flag): 
export async function middleware({ params, request, context }: Route.MiddlewareArgs) {
  // Middleware logic
}

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Route.ClientMiddlewareArgs

Arguments for client middleware: 
export async function clientMiddleware({ params, request, context }: Route.ClientMiddlewareArgs) {
  // Client middleware logic
}

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Route Parameters

Parameters are automatically typed based on route paths: 
// routes.ts
import { route } from "@react-router/dev/routes";

export default [
  route("posts/:postId/comments/:commentId", "./post-comment.tsx"),
];

// app/post-comment.tsx
import type { Route } from "./+types/post-comment";

export async function loader({ params }: Route.LoaderArgs) {
  // params.postId: string
  // params.commentId: string
  const { postId, commentId } = params;
}

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Loader Data Types

Loader return values are automatically inferred: 
export async function loader() {
  const posts = await db.post.findMany();
  return { posts }; // Type is inferred
}

export default function Posts({ loaderData }: Route.ComponentProps) {
  // loaderData.posts has the correct type
  return (
    <ul>
      {loaderData.posts.map((post) => (
        <li key={post.id}>{post.title}</li>
      ))}
    </ul>
  );
}

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Action Data Types

Action return values are also typed: 
export async function action({ request }: Route.ActionArgs) {
  const formData = await request.formData();
  const post = await createPost(formData);
  return { post, success: true };
}

export default function NewPost({ actionData }: Route.ComponentProps) {
  // actionData?.post and actionData?.success are typed
  if (actionData?.success) {
    return <p>Post created: {actionData.post.title}</p>;
  }
}

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Manual Type Generation

Run type generation manually: 
npx react-router typegen

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Watch Mode

Types are automatically regenerated during development when:
  • Route files are added or removed
  • routes.ts configuration changes
  • react-router.config.ts changes

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Future Flags Types

Future flags are typed in .react-router/types/react-router-config.d.ts: 
// Generated based on your config
declare module "react-router" {
  interface Future {
    v8_middleware: true; // or false based on your config
    v8_splitRouteModules: false;
    v8_viteEnvironmentApi: false;
  }
}
This enables conditional types based on enabled features.

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Server Build Types

The server build exports are typed in +server.d.ts: 
import type { ServerBuild } from "react-router";

// Type for your server build
export const build: ServerBuild;

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Middleware Types

With middleware enabled: 
export default {
  future: {
    v8_middleware: true,
  },
} satisfies Config;
You get typed middleware functions: 
import type { Route } from "./+types/route-name";

export const middleware: Route.MiddlewareFunction = async ({ params, request, context }) => {
  // All arguments are typed
};

export const clientMiddleware: Route.ClientMiddlewareFunction = async ({ params, request, context }) => {
  // Client middleware types
};

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Type Safety Best Practices

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1. Use Route Types

Always import and use the generated route types: 
import type { Route } from "./+types/route-name";

export async function loader(args: Route.LoaderArgs) {
  // Typed automatically
}

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2. Type Return Values Explicitly

For complex return types, add explicit types: 
interface LoaderData {
  posts: Post[];
  page: number;
  totalPages: number;
}

export async function loader(): Promise<LoaderData> {
  // Return type is explicit
  return {
    posts: await getPosts(),
    page: 1,
    totalPages: 10,
  };
}

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3. Use Type Guards

For error boundaries: 
export function ErrorBoundary({ error }: Route.ErrorBoundaryProps) {
  if (error instanceof Error) {
    return <div>Error: {error.message}</div>;
  }
  return <div>Unknown error</div>;
}

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Troubleshooting

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Types Not Updating

  1. Check that .react-router/types is included in tsconfig.json
  2. Restart your TypeScript server in VS Code (Cmd+Shift+P > “Restart TS Server”)
  3. Run npx react-router typegen manually

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Build Errors

If types cause build errors:
  1. Delete .react-router/types directory
  2. Run npx react-router typegen
  3. Restart your IDE

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Missing Types

If route types are missing:
  1. Ensure the route file exists
  2. Check routes.ts configuration is valid
  3. Look for errors in the console

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See Also

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