---
title: createBrowserRouter
---
# createBrowserRouter
[MODES: data]
## Summary
[Reference Documentation ↗](https://api.reactrouter.com/v7/functions/react_router.createBrowserRouter.html)
Create a new [data router](https://api.reactrouter.com/v7/interfaces/react_router.DataRouter.html) that manages the application
path via [`history.pushState`](https://developer.mozilla.org/en-US/docs/Web/API/History/pushState)
and [`history.replaceState`](https://developer.mozilla.org/en-US/docs/Web/API/History/replaceState).
## Signature
```tsx
function createBrowserRouter(
routes: RouteObject[],
opts?: DOMRouterOpts,
): DataRouter
```
## Params
### routes
Application routes
### opts.basename
Basename path for the application.
### opts.dataStrategy
Override the default data strategy of running loaders in parallel.
See [`DataStrategyFunction`](https://api.reactrouter.com/v7/interfaces/react_router.DataStrategyFunction.html).
This is a low-level API intended for advanced use-cases. This
overrides React Router's internal handling of
[`action`](../../start/data/route-object#action)/[`loader`](../../start/data/route-object#loader)
execution, and if done incorrectly will break your app code. Please use
with caution and perform the appropriate testing.
By default, React Router is opinionated about how your data is loaded/submitted -
and most notably, executes all of your [`loader`](../../start/data/route-object#loader)s
in parallel for optimal data fetching. While we think this is the right
behavior for most use-cases, we realize that there is no "one size fits all"
solution when it comes to data fetching for the wide landscape of
application requirements.
The `dataStrategy` option gives you full control over how your [`action`](../../start/data/route-object#action)s
and [`loader`](../../start/data/route-object#loader)s are executed and lays
the foundation to build in more advanced APIs such as middleware, context,
and caching layers. Over time, we expect that we'll leverage this API
internally to bring more first class APIs to React Router, but until then
(and beyond), this is your way to add more advanced functionality for your
application's data needs.
The `dataStrategy` function should return a key/value-object of
`routeId` -> [`DataStrategyResult`](https://api.reactrouter.com/v7/interfaces/react_router.DataStrategyResult.html) and should include entries for any
routes where a handler was executed. A `DataStrategyResult` indicates if
the handler was successful or not based on the `DataStrategyResult.type`
field. If the returned `DataStrategyResult.result` is a [`Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response),
React Router will unwrap it for you (via [`res.json`](https://developer.mozilla.org/en-US/docs/Web/API/Response/json)
or [`res.text`](https://developer.mozilla.org/en-US/docs/Web/API/Response/text)).
If you need to do custom decoding of a [`Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response)
but want to preserve the status code, you can use the `data` utility to
return your decoded data along with a `ResponseInit`.
Example dataStrategy Use Cases
**Adding logging**
In the simplest case, let's look at hooking into this API to add some logging
for when our route [`action`](../../start/data/route-object#action)s/[`loader`](../../start/data/route-object#loader)s
execute:
```tsx
let router = createBrowserRouter(routes, {
async dataStrategy({ matches, request }) {
const matchesToLoad = matches.filter((m) => m.shouldLoad);
const results: Record = {};
await Promise.all(
matchesToLoad.map(async (match) => {
console.log(`Processing ${match.route.id}`);
results[match.route.id] = await match.resolve();;
})
);
return results;
},
});
```
**Middleware**
Let's define a middleware on each route via [`handle`](../../start/data/route-object#handle)
and call middleware sequentially first, then call all
[`loader`](../../start/data/route-object#loader)s in parallel - providing
any data made available via the middleware:
```ts
const routes = [
{
id: "parent",
path: "/parent",
loader({ request }, context) {
// ...
},
handle: {
async middleware({ request }, context) {
context.parent = "PARENT MIDDLEWARE";
},
},
children: [
{
id: "child",
path: "child",
loader({ request }, context) {
// ...
},
handle: {
async middleware({ request }, context) {
context.child = "CHILD MIDDLEWARE";
},
},
},
],
},
];
let router = createBrowserRouter(routes, {
async dataStrategy({ matches, params, request }) {
// Run middleware sequentially and let them add data to `context`
let context = {};
for (const match of matches) {
if (match.route.handle?.middleware) {
await match.route.handle.middleware(
{ request, params },
context
);
}
}
// Run loaders in parallel with the `context` value
let matchesToLoad = matches.filter((m) => m.shouldLoad);
let results = await Promise.all(
matchesToLoad.map((match, i) =>
match.resolve((handler) => {
// Whatever you pass to `handler` will be passed as the 2nd parameter
// to your loader/action
return handler(context);
})
)
);
return results.reduce(
(acc, result, i) =>
Object.assign(acc, {
[matchesToLoad[i].route.id]: result,
}),
{}
);
},
});
```
**Custom Handler**
It's also possible you don't even want to define a [`loader`](../../start/data/route-object#loader)
implementation at the route level. Maybe you want to just determine the
routes and issue a single GraphQL request for all of your data? You can do
that by setting your `route.loader=true` so it qualifies as "having a
loader", and then store GQL fragments on `route.handle`:
```ts
const routes = [
{
id: "parent",
path: "/parent",
loader: true,
handle: {
gql: gql`
fragment Parent on Whatever {
parentField
}
`,
},
children: [
{
id: "child",
path: "child",
loader: true,
handle: {
gql: gql`
fragment Child on Whatever {
childField
}
`,
},
},
],
},
];
let router = createBrowserRouter(routes, {
async dataStrategy({ matches, params, request }) {
// Compose route fragments into a single GQL payload
let gql = getFragmentsFromRouteHandles(matches);
let data = await fetchGql(gql);
// Parse results back out into individual route level `DataStrategyResult`'s
// keyed by `routeId`
let results = parseResultsFromGql(data);
return results;
},
});
```
### opts.future
Future flags to enable for the router.
### opts.getContext
A function that returns an [`RouterContextProvider`](../utils/RouterContextProvider) instance
which is provided as the `context` argument to client [`action`](../../start/data/route-object#action)s,
[`loader`](../../start/data/route-object#loader)s and [middleware](../../how-to/middleware).
This function is called to generate a fresh `context` instance on each
navigation or fetcher call.
```tsx
import {
createContext,
RouterContextProvider,
} from "react-router";
const apiClientContext = createContext();
function createBrowserRouter(routes, {
getContext() {
let context = new RouterContextProvider();
context.set(apiClientContext, getApiClient());
return context;
}
})
```
### opts.hydrationData
When Server-Rendering and opting-out of automatic hydration, the
`hydrationData` option allows you to pass in hydration data from your
server-render. This will almost always be a subset of data from the
[`StaticHandlerContext`](https://api.reactrouter.com/v7/interfaces/react_router.StaticHandlerContext.html) value you get back from the [`StaticHandler`](https://api.reactrouter.com/v7/interfaces/react_router.StaticHandler.html)'s
`query` method:
```tsx
const router = createBrowserRouter(routes, {
hydrationData: {
loaderData: {
// [routeId]: serverLoaderData
},
// may also include `errors` and/or `actionData`
},
});
```
**Partial Hydration Data**
You will almost always include a complete set of `loaderData` to hydrate a
server-rendered app. But in advanced use-cases (such as Framework Mode's
[`clientLoader`](../../start/framework/route-module#clientLoader)), you may
want to include `loaderData` for only some routes that were loaded/rendered
on the server. This allows you to hydrate _some_ of the routes (such as the
app layout/shell) while showing a `HydrateFallback` component and running
the [`loader`](../../start/data/route-object#loader)s for other routes
during hydration.
A route [`loader`](../../start/data/route-object#loader) will run during
hydration in two scenarios:
1. No hydration data is provided
In these cases the `HydrateFallback` component will render on initial
hydration
2. The `loader.hydrate` property is set to `true`
This allows you to run the [`loader`](../../start/data/route-object#loader)
even if you did not render a fallback on initial hydration (i.e., to
prime a cache with hydration data)
```tsx
const router = createBrowserRouter(
[
{
id: "root",
loader: rootLoader,
Component: Root,
children: [
{
id: "index",
loader: indexLoader,
HydrateFallback: IndexSkeleton,
Component: Index,
},
],
},
],
{
hydrationData: {
loaderData: {
root: "ROOT DATA",
// No index data provided
},
},
}
);
```
### opts.patchRoutesOnNavigation
Lazily define portions of the route tree on navigations.
See [`PatchRoutesOnNavigationFunction`](https://api.reactrouter.com/v7/types/react_router.PatchRoutesOnNavigationFunction.html).
By default, React Router wants you to provide a full route tree up front via
`createBrowserRouter(routes)`. This allows React Router to perform synchronous
route matching, execute loaders, and then render route components in the most
optimistic manner without introducing waterfalls. The tradeoff is that your
initial JS bundle is larger by definition — which may slow down application
start-up times as your application grows.
To combat this, we introduced [`route.lazy`](../../start/data/route-object#lazy)
in [v6.9.0](https://github.com/remix-run/react-router/blob/main/CHANGELOG.md#v690)
which lets you lazily load the route _implementation_ ([`loader`](../../start/data/route-object#loader),
[`Component`](../../start/data/route-object#Component), etc.) while still
providing the route _definition_ aspects up front (`path`, `index`, etc.).
This is a good middle ground. React Router still knows about your route
definitions (the lightweight part) up front and can perform synchronous
route matching, but then delay loading any of the route implementation
aspects (the heavier part) until the route is actually navigated to.
In some cases, even this doesn't go far enough. For huge applications,
providing all route definitions up front can be prohibitively expensive.
Additionally, it might not even be possible to provide all route definitions
up front in certain Micro-Frontend or Module-Federation architectures.
This is where `patchRoutesOnNavigation` comes in ([RFC](https://github.com/remix-run/react-router/discussions/11113)).
This API is for advanced use-cases where you are unable to provide the full
route tree up-front and need a way to lazily "discover" portions of the route
tree at runtime. This feature is often referred to as ["Fog of War"](https://en.wikipedia.org/wiki/Fog_of_war),
because similar to how video games expand the "world" as you move around -
the router would be expanding its routing tree as the user navigated around
the app - but would only ever end up loading portions of the tree that the
user visited.
`patchRoutesOnNavigation` will be called anytime React Router is unable to
match a `path`. The arguments include the `path`, any partial `matches`,
and a `patch` function you can call to patch new routes into the tree at a
specific location. This method is executed during the `loading` portion of
the navigation for `GET` requests and during the `submitting` portion of
the navigation for non-`GET` requests.
Example patchRoutesOnNavigation Use Cases
**Patching children into an existing route**
```tsx
const router = createBrowserRouter(
[
{
id: "root",
path: "/",
Component: RootComponent,
},
],
{
async patchRoutesOnNavigation({ patch, path }) {
if (path === "/a") {
// Load/patch the `a` route as a child of the route with id `root`
let route = await getARoute();
// ^ { path: 'a', Component: A }
patch("root", [route]);
}
},
}
);
```
In the above example, if the user clicks a link to `/a`, React Router
won't match any routes initially and will call `patchRoutesOnNavigation`
with a `path = "/a"` and a `matches` array containing the root route
match. By calling `patch('root', [route])`, the new route will be added
to the route tree as a child of the `root` route and React Router will
perform matching on the updated routes. This time it will successfully
match the `/a` path and the navigation will complete successfully.
**Patching new root-level routes**
If you need to patch a new route to the top of the tree (i.e., it doesn't
have a parent), you can pass `null` as the `routeId`:
```tsx
const router = createBrowserRouter(
[
{
id: "root",
path: "/",
Component: RootComponent,
},
],
{
async patchRoutesOnNavigation({ patch, path }) {
if (path === "/root-sibling") {
// Load/patch the `/root-sibling` route as a sibling of the root route
let route = await getRootSiblingRoute();
// ^ { path: '/root-sibling', Component: RootSibling }
patch(null, [route]);
}
},
}
);
```
**Patching subtrees asynchronously**
You can also perform asynchronous matching to lazily fetch entire sections
of your application:
```tsx
let router = createBrowserRouter(
[
{
path: "/",
Component: Home,
},
],
{
async patchRoutesOnNavigation({ patch, path }) {
if (path.startsWith("/dashboard")) {
let children = await import("./dashboard");
patch(null, children);
}
if (path.startsWith("/account")) {
let children = await import("./account");
patch(null, children);
}
},
}
);
```
If in-progress execution of `patchRoutesOnNavigation` is
interrupted by a later navigation, then any remaining `patch` calls in
the interrupted execution will not update the route tree because the
operation was cancelled.
**Co-locating route discovery with route definition**
If you don't wish to perform your own pseudo-matching, you can leverage
the partial `matches` array and the [`handle`](../../start/data/route-object#handle)
field on a route to keep the children definitions co-located:
```tsx
let router = createBrowserRouter(
[
{
path: "/",
Component: Home,
},
{
path: "/dashboard",
children: [
{
// If we want to include /dashboard in the critical routes, we need to
// also include it's index route since patchRoutesOnNavigation will not be
// called on a navigation to `/dashboard` because it will have successfully
// matched the `/dashboard` parent route
index: true,
// ...
},
],
handle: {
lazyChildren: () => import("./dashboard"),
},
},
{
path: "/account",
children: [
{
index: true,
// ...
},
],
handle: {
lazyChildren: () => import("./account"),
},
},
],
{
async patchRoutesOnNavigation({ matches, patch }) {
let leafRoute = matches[matches.length - 1]?.route;
if (leafRoute?.handle?.lazyChildren) {
let children =
await leafRoute.handle.lazyChildren();
patch(leafRoute.id, children);
}
},
}
);
```
**A note on routes with parameters**
Because React Router uses ranked routes to find the best match for a
given path, there is an interesting ambiguity introduced when only a
partial route tree is known at any given point in time. If we match a
fully static route such as `path: "/about/contact-us"` then we know we've
found the right match since it's composed entirely of static URL segments.
Thus, we do not need to bother asking for any other potentially
higher-scoring routes.
However, routes with parameters (dynamic or splat) can't make this
assumption because there might be a not-yet-discovered route that scores
higher. Consider a full route tree such as:
```tsx
// Assume this is the full route tree for your app
const routes = [
{
path: "/",
Component: Home,
},
{
id: "blog",
path: "/blog",
Component: BlogLayout,
children: [
{ path: "new", Component: NewPost },
{ path: ":slug", Component: BlogPost },
],
},
];
```
And then assume we want to use `patchRoutesOnNavigation` to fill this in
as the user navigates around:
```tsx
// Start with only the index route
const router = createBrowserRouter(
[
{
path: "/",
Component: Home,
},
],
{
async patchRoutesOnNavigation({ patch, path }) {
if (path === "/blog/new") {
patch("blog", [
{
path: "new",
Component: NewPost,
},
]);
} else if (path.startsWith("/blog")) {
patch("blog", [
{
path: ":slug",
Component: BlogPost,
},
]);
}
},
}
);
```
If the user were to a blog post first (i.e., `/blog/my-post`) we would
patch in the `:slug` route. Then, if the user navigated to `/blog/new` to
write a new post, we'd match `/blog/:slug` but it wouldn't be the _right_
match! We need to call `patchRoutesOnNavigation` just in case there
exists a higher-scoring route we've not yet discovered, which in this
case there is.
So, anytime React Router matches a path that contains at least one param,
it will call `patchRoutesOnNavigation` and match routes again just to
confirm it has found the best match.
If your `patchRoutesOnNavigation` implementation is expensive or making
side effect [`fetch`](https://developer.mozilla.org/en-US/docs/Web/API/fetch)
calls to a backend server, you may want to consider tracking previously
seen routes to avoid over-fetching in cases where you know the proper
route has already been found. This can usually be as simple as
maintaining a small cache of prior `path` values for which you've already
patched in the right routes:
```tsx
let discoveredRoutes = new Set();
const router = createBrowserRouter(routes, {
async patchRoutesOnNavigation({ patch, path }) {
if (discoveredRoutes.has(path)) {
// We've seen this before so nothing to patch in and we can let the router
// use the routes it already knows about
return;
}
discoveredRoutes.add(path);
// ... patch routes in accordingly
},
});
```
### opts.window
[`Window`](https://developer.mozilla.org/en-US/docs/Web/API/Window) object
override. Defaults to the global `window` instance.
## Returns
An initialized [data router](https://api.reactrouter.com/v7/interfaces/react_router.DataRouter.html) to pass to [``](../data-routers/RouterProvider)