Routing

Functions utilize file-based routing. Your /functions directory structure determines the designated routes that your Functions will run on. You can create a /functions directory with as many levels as needed for your project's use case. Review the following directory:

The following routes will be generated based on the above file structure. These routes map the URL pattern to the /functions file that will be invoked when a visitor goes to the URL:

If no Function is matched, it will fall back to a static asset if there is one. Otherwise, the Function will fall back to the default routing behavior for Pages' static assets.

Dynamic routes allow you to match URLs with parameterized segments. This can be useful if you are building dynamic applications. You can accept dynamic values which map to a single path by changing your filename.

To create a dynamic route, place one set of brackets around your filename – for example, /users/[user].js. By doing this, you are creating a placeholder for a single path segment:

By placing two sets of brackets around your filename – for example, /users/[[user]].js – you are matching any depth of route after /users/:

Review the following /functions/ directory structure:

The following requests will match the following files:

The URL segment(s) that match the placeholder ([user]) will be available in the request context object. The context.params object can be used to find the matched value for a given filename placeholder.

For files which match a single URL segment (use a single set of brackets), the values are returned as a string:

export function onRequest(context) {
	return new Response(context.params.user);
}

The above logic will return daniel for requests to /users/daniel.

For files which match against multiple URL segments (use a double set of brackets), the values are returned as an array:

export function onRequest(context) {
	return new Response(JSON.stringify(context.params.catchall));
}

The above logic will return ["daniel", "xyz", "123"] for requests to /users/daniel/xyz/123.

On a purely static project, Pages offers unlimited free requests. However, once you add Functions on a Pages project, all requests by default will invoke your Function. To continue receiving unlimited free static requests, exclude your project's static routes by creating a _routes.json file. This file will be automatically generated if a functions directory is detected in your project when you publish your project with Pages CI or Wrangler.

Create a _routes.json file to control when your Function is invoked. It should be placed in the build directory of your project.

This file will include three different properties:

• version: Defines the version of the schema. Currently there is only one version of the schema (version 1), however, we may add more in the future and aim to be backwards compatible.
• include: Defines routes that will be invoked by Functions. Accepts wildcard behavior.
• exclude: Defines routes that will not be invoked by Functions. Accepts wildcard behavior. exclude always take priority over include.

Below is an example of a _routes.json.

{
	"version": 1,
	"include": ["/*"],
	"exclude": []
}

This _routes.json will invoke your Functions on all routes.

Below is another example of a _routes.json file. Any route inside the /build directory will not invoke the Function and will not incur a Functions invocation charge.

{
	"version": 1,
	"include": ["/*"],
	"exclude": ["/build/*"]
}

If on the Workers Free plan, you can configure how Pages behaves when your daily free tier allowance of Pages Functions requests is exhausted. If, for example, you are performing authentication checks or other critical functionality in your Pages Functions, you may wish to disable your Pages project when the allowance is exhausted.

1. In the Cloudflare dashboard, go to the Workers & Pages page.

   Go to Workers & Pages ↗

2. Select your Pages project.

3. Go to Settings > Runtime > Fail open / closed.

"Fail open" means that static assets will continue to be served, even if Pages Functions would ordinarily have run first. "Fail closed" means an error page will be returned, rather than static assets.

The daily request limit for Pages Functions can be removed entirely by upgrading to Workers Standard.

Functions invocation routes have the following limits:

• You must have at least one include rule.
• You may have no more than 100 include/exclude rules combined.
• Each rule may have no more than 100 characters.