file-routing.md

description	Routes are the basic building block of Fresh applications. They are used to define the behaviour the application when a given path is requested.

Use the .fsRoutes() helper on the App instance to specify where file based routes should be inserted. It adds routes based on the structure in the routes/ folder in your project (or any other folder you have set in dev.ts). When you add a new file there, it will register a new route automatically.

import { Builder } from "fresh/dev";

// Optionally set a custom route dir (will be `<root>/routes` by default)
const builder = new Builder({ routeDir: "path/to/routes" });

if (Deno.args.includes("build")) {
  await builder.build();
} else {
  await builder.listen(() => import("./main.ts"));
}

import { App, staticFiles } from "fresh";

const app = new App({ root: import.meta.url })
  .use(staticFiles())
  .fsRoutes(); // This inserts all file based routes here

[info]: The staticFiles() middleware is required when using file based routing. Otherwise the necessary JavaScript files for islands won't be served to the browser.

Example project structure:

├── deno.json
├── main.ts
├── dev.ts
└── routes
    ├── (marketing)  # Route group, used to group related routes
    │   ├── _layout.tsx  # Apply layout to all routes in this directory
    │   ├── about.tsx    # /about route
    │   ├── career.tsx   # /career route
    │   ├── (_components)  # related components
    │   │   └── newsletter-cta.tsx
    │   └── (_islands)  # Local island directory
    │       └── interactive-stats.tsx # Fresh treats this as an island
    └── shop
        ├── (_components)
        │   └── product-card.tsx
        ├── (_islands)
        │   └── cart.tsx # Fresh treats this as an island
        └── index.tsx

File names are mapped to route patterns as follows:

• File extensions are ignored.
• Literals in the file path are treated as string literals to match.
• Files named <path>/index.<ext> behave identically to a file named <path>.<ext>.
• Path segments can be made dynamic by surrounding an identifier with [ and ].
• Paths where the last path segment follows the structure [...<ident>] are treated as having a wildcard suffix.

Here is a table of file names, which route patterns they map to, and which paths they might match:

File name	Route pattern	Matching paths
index.ts	/	/
about.ts	/about	/about
blog/index.ts	/blog	/blog
blog/[slug].ts	/blog/:slug	/blog/foo, /blog/bar
blog/[slug]/comments.ts	/blog/:slug/comments	/blog/foo/comments
old/[...path].ts	/old/:path*	/old/foo, /old/bar/baz
docs/[[version]]/index.ts	/docs{/:version}?	/docs, /docs/latest, /docs/canary

Advanced use-cases can require that a more complex pattern be used for matching. A custom URL pattern can be specified in the route configuration. This pattern will be used instead of the file path based pattern:

import { RouteConfig } from "fresh";

export const config: RouteConfig = {
  routeOverride: "/x/:module@:version/:path*",
};

// ...

Route Groups

When working with layouts or middlewares, you'll sometimes come across a situation where you want your routes to inherit from a layout other than what's suggested by the URL segment.

Let's illustrate that with an example:

/about -> layout A
/career -> layout A
/archive -> layout B
/contact -> layout B

Without any way to group routes this is a problem because every route segment can only have one _layout file.

└── routes
    ├── _layout.tsx  # applies to all routes here :(
    ├── about.tsx
    ├── career.tsx
    ├── archive.tsx
    └── contact.tsx

We can solve this problem with route groups. A route group is a folder which has a name that is wrapped in parentheses. For example (info) would be considered a route group and so would (marketing). This enables us to group related routes in a folder and use a different _layout file for each group.

└── routes
    ├── (marketing)
    │   ├── _layout.tsx  # only applies to about.tsx and career.tsx
    │   ├── about.tsx
    │   └── career.tsx
    └── (info)
        ├── _layout.tsx  # only applies to archive.tsx and contact.tsx
        ├── archive.tsx
        └── contact.tsx

[warn]: Be careful about routes in different groups which match to the same URL. Such scenarios will lead to ambiguity as to which route file should be picked.

└── routes
    ├── (group-1)
    │   └── about.tsx  # Bad: Maps to same `/about` url
    └── (group-2)
        └── about.tsx  # Bad: Maps to same `/about` url