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Configure hosting behavior

With Firebase Hosting, you can configure customized hosting behavior for requests to your site.

What can you configure for Hosting?

  • Specify which files in your local project directory you want to deploy to Firebase Hosting. Learn how.

  • Serve a customized 404/Not Found page. Learn how.

  • Set up redirects for pages that you've moved or deleted. Learn how.

  • Set up rewrites for any of these purposes:

    • Show the same content for multiple URLs. Learn how.

    • Serve a function or access a Cloud Run container from a Hosting URL. Learn how: function or container.

    • Create a custom domain Dynamic Link. Learn how.

  • Add headers to pass along additional information about a request or a response, such as how browsers should handle the page and its content (authentication, caching, encoding, etc.). Learn how.

  • Set up internationalization (i18n) rewrites to serve specific content based on a user's language preference and/or country. Learn how (different page).

Where do you define your Hosting configuration?

You define your Firebase Hosting configuration in your firebase.json file. Firebase automatically creates your firebase.json file at the root of your project directory when you run the firebase init command.

You can find a full firebase.json configuration example (covering only Firebase Hosting) at the bottom of this page. Note that a firebase.json file can also contain configurations for other Firebase services.

You can check the deployed firebase.json content using the Hosting REST API.

Priority order of Hosting responses

The different Firebase Hosting configuration options described on this page can sometimes overlap. If there is a conflict, Hosting determines its response using the following priority order:

  1. Reserved namespaces that begin with a /__/* path segment
  2. Configured redirects
  3. Exact-match static content
  4. Configured rewrites
  5. Custom 404 page
  6. Default 404 page

If you're using i18n rewrites, the exact-match and 404 handling priority order are expanded in scope to accommodate your "i18n content".

Specify which files to deploy

The default attributes — public and ignore — included in the default firebase.json file define which files in your project directory should be deployed to your Firebase project.

The default hosting configuration in a firebase.json file looks like this:

"hosting": {
  "public": "public",  // the only required attribute for Hosting
  "ignore": [
    "firebase.json",
    "**/.*",
    "**/node_modules/**"
  ]
}

public

Required
The public attribute specifies which directory to deploy to Firebase Hosting. The default value is a directory named public, but you can specify any directory's path, as long as it exists in your project directory.

The following is the default specified name of the directory to deploy:

"hosting": {
  "public": "public"

  // ...
}

You can change the default value to the directory that you want to deploy:

"hosting": {
  "public": "dist/app"

  // ...
}

ignore

Optional
The ignore attribute specifies the files to ignore on deploy. It can take globs the same way that Git handles .gitignore.

The following are the default values for the files to ignore:

"hosting": {
  // ...

  "ignore": [
    "firebase.json",  // the Firebase configuration file (the file described on this page)
    "**/.*",  // files with a leading period should be hidden from the system
    "**/node_modules/**"  // contains dependencies used to create your site but not run it
  ]
}

Customize a 404/Not Found page

Optional
You can serve a custom 404 Not Found error when a user tries to access a page that doesn't exist.

Create a new file in your project's public directory, name it 404.html, then add your custom 404 Not Found content to the file.

Firebase Hosting will display the content of this custom 404.html page if a browser triggers a 404 Not Found error on your domain or subdomain.

Configure redirects

Optional
Use a URL redirect to prevent broken links if you've moved a page or to shorten URLs. For example, you could redirect a browser from example.com/team to example.com/about.html.

Specify URL redirects by creating a redirects attribute that contains an array of objects (called "redirect rules"). In each rule, specify a URL pattern that, if matched to the request URL path, triggers Hosting to respond with a redirect to the specified destination URL.

Here's the basic structure for a redirects attribute. This example redirects requests to /foo by making a new request to /bar.

"hosting": {
  // ...

  // Returns a permanent redirect to "/bar" for requests to "/foo" (but not "/foo/**")
  "redirects": [ {
    "source": "/foo",
    "destination": "/bar",
    "type": 301
  } ]
}

The redirects attribute contains an array of redirect rules, where each rule must include the fields in the table below.

Firebase Hosting compares the source or regex value against all URL paths at the start of every request (before the browser determines whether a file or folder exists at that path). If a match is found, then the Firebase Hosting origin server sends an HTTP redirect response telling the browser to make a new request at the destination URL.

Field Description
redirects
source (recommended)
or regex

A URL pattern that, if matched to the initial request URL, triggers Hosting to apply the redirect

destination

A static URL where the browser should make a new request

This URL can be a relative or an absolute path.

type

The HTTP response code

  • Use a type of 301 for 'Moved Permanently'
  • Use a type of 302 for 'Found' (Temporary Redirect)

Capture URL segments for redirects

Optional
Sometimes, you might need to capture specific segments of a redirect rule's URL pattern (source or regex value), then re-use these segments in the rule's destination path.

Configure rewrites

Optional
Use a rewrite to show the same content for multiple URLs. Rewrites are particularly useful with pattern matching, as you can accept any URL that matches the pattern and let the client-side code decide what to display.

You can also use rewrites to support apps that use HTML5 pushState for navigation. When a browser attempts to open a URL path that matches the specified source or regex URL pattern, the browser will be given the contents of the file at the destination URL instead.

Specify URL rewrites by creating a rewrites attribute that contains an array of objects (called "rewrite rules"). In each rule, specify a URL pattern that, if matched to the request URL path, triggers Hosting to respond as if the service were given the specified destination URL.

Here's the basic structure for a rewrites attribute. This example serves index.html for requests to files or directories that don't exist.

"hosting": {
  // ...

  // Serves index.html for requests to files or directories that do not exist
  "rewrites": [ {
    "source": "**",
    "destination": "/index.html"
  } ]
}

The rewrites attribute contains an array of rewrite rules, where each rule must include the fields in the table below.

Firebase Hosting only applies a rewrite rule if a file or directory does not exist at a URL path that matches the specified source or regex URL pattern. When a request triggers a rewrite rule, the browser returns the actual content of the specified destination file instead of an HTTP redirect.

Field Description
rewrites
source (recommended)
or regex

A URL pattern that, if matched to the initial request URL, triggers Hosting to apply the rewrite

destination

A local file that must exist

This URL can be a relative or an absolute path.

Direct requests to a function

You can use rewrites to serve a function from a Firebase Hosting URL. The following example is an excerpt from serving dynamic content using Cloud Functions.

For example, to direct all requests from the page /bigben on your Hosting site to execute the bigben function:

"hosting": {
  // ...

  // Directs all requests from the page `/bigben` to execute the `bigben` function
  "rewrites": [ {
    "source": "/bigben",
    "function": "bigben"
  } ]
}

After adding this rewrite rule and deploying to Firebase (using firebase deploy), your function is reachable via the following URLs:

  • Your Firebase subdomains:
    PROJECT_ID.web.app/bigben and PROJECT_ID.firebaseapp.com/bigben

  • Any connected custom domains:
    CUSTOM_DOMAIN/bigben

Direct requests to a Cloud Run container

You can use rewrites to access a Cloud Run container from a Firebase Hosting URL. The following example is an excerpt from serving dynamic content using Cloud Run.

For example, to direct all requests from the page /helloworld on your Hosting site to trigger the startup and running of a helloworld container instance:

"hosting": {
 // ...

 // Directs all requests from the page `/helloworld` to trigger and run a `helloworld` container
 "rewrites": [ {
   "source": "/helloworld",
   "run": {
     "serviceId": "helloworld",  // "service name" (from when you deployed the container image)
     "region": "us-central1"  // optional (if omitted, default is us-central1)
   }
 } ]
}

After adding this rewrite rule and deploying to Firebase (using firebase deploy), your container image is reachable via the following URLs:

  • Your Firebase subdomains:
    PROJECT_ID.web.app/helloworld and PROJECT_ID.firebaseapp.com/helloworld

  • Any connected custom domains:
    CUSTOM_DOMAIN/helloworld

You can use rewrites to create custom domain Dynamic Links. Visit the Dynamic Links documentation for detailed information about setting up a custom domain for Dynamic Links.

  • Use your custom domain only for Dynamic Links

    "hosting": {
      // ...
    
      "appAssociation": "AUTO",  // required for Dynamic Links (default is AUTO if not specified)
    
      // Add the "rewrites" attribute within "hosting"
      "rewrites": [ {
        "source": "/**",  // the Dynamic Links start with "https://CUSTOM_DOMAIN/"
        "dynamicLinks": true
      } ]
    }
    
  • Specify custom domain path prefixes to use for Dynamic Links

    "hosting": {
      // ...
    
      "appAssociation": "AUTO",  // required for Dynamic Links (default is AUTO if not specified)
    
      // Add the "rewrites" attribute within "hosting"
      "rewrites": [ {
        "source": "/promos/**",  // the Dynamic Links start with "https://CUSTOM_DOMAIN/promos/"
        "dynamicLinks": true
      }, {
        "source": "/links/share/**",  // the Dynamic Links start with "https://CUSTOM_DOMAIN/links/share/"
        "dynamicLinks": true
      } ]
    }
    

Configuring Dynamic Links in your firebase.json file requires the following:

Field Description
appAssociation

Must be set to AUTO

  • If you don't include this attribute in your configuration, the default for appAssociation is AUTO.
  • By setting this attribute to AUTO, Hosting can dynamically generate assetlinks.json and apple-app-site-association files when they're requested.
rewrites
source

A path that you want to use for Dynamic Links

Unlike rules that rewrite paths to URLs, rewrite rules for Dynamic Links can't contain regular expressions.

dynamicLinks Must be set to true

Configure headers

Optional
Headers allow the client and the server to pass additional information along with a request or a response. Some sets of headers can affect how the browser handles the page and its content, including access control, authentication, caching, and encoding.

Specify custom, file-specific response headers by creating a headers attribute that contains an array of header objects. In each object, specify a URL pattern that, if matched to the request URL path, triggers Hosting to apply the specified custom response headers.

Here's the basic structure for a headers attribute. This example applies a CORS header for all font files.

"hosting": {
  // ...

  // Applies a CORS header for all font files
  "headers": [ {
    "source": "**/*.@(eot|otf|ttf|ttc|woff|font.css)",
    "headers": [ {
      "key": "Access-Control-Allow-Origin",
      "value": "*"
    } ]
  } ]
}

The headers attribute contains an array of definitions, where each definition must include the fields in the table below.

Field Description
headers
source (recommended)
or regex

A URL pattern that, if matched to the initial request URL, triggers Hosting to apply the custom header

To create a header to match against your custom 404 page, use 404.html as your source or regex value.

array of (sub-)headers

The custom headers that Hosting applies to the request path

Each sub-header must include a key and value pair (see next two rows).

key The name of the header, for example Cache-Control
value The value for the header, for example max-age=7200

You can learn more about Cache-Control in the Hosting section that describes serving dynamic content and hosting microservices. You can also learn more about CORS headers.

Control .html extensions

Optional
The cleanUrls attribute allows you to control whether or not URLs should include the .html extension.

When true, Hosting automatically drops the .html extension from uploaded file URLs. If an .html extension is added in the request, Hosting performs a 301 redirect to the same path but eliminates the .html extension.

Here's how to control the inclusion of .html in URLs by including a cleanUrls attribute:

"hosting": {
  // ...

  // Drops `.html` from uploaded URLs
  "cleanUrls": true
}

Control trailing slashes

Optional
The trailingSlash attribute allows you to control whether or not static content URLs should include trailing slashes.

  • When true, Hosting redirects URLs to add a trailing slash.
  • When false, Hosting redirects URLs to remove a trailing slash.
  • When unspecified, Hosting only uses trailing slashes for directory index files (for example, about/index.html).

Here's how to control trailing slashes by adding a trailingSlash attribute:

"hosting": {
  // ...

  // Removes trailing slashes from URLs
  "trailingSlash": false
}

The trailingSlash attribute does not affect rewrites to dynamic content served by Cloud Functions or Cloud Run.

Glob pattern matching

Firebase Hosting configuration options make extensive use of the glob pattern matching notation with extglob, similar to how Git handles gitignore rules and Bower handles ignore rules. This wiki page is a more detailed reference, but the following are explanations of examples used on this page:

  • firebase.json — Only matches the firebase.json file in the root of the public directory

  • ** — Matches any file or folder in an arbitrary sub-directory

  • * — Only matches files and folders in the root of the public directory

  • **/.* — Matches any file beginning with . (usually hidden files, like in the .git folder) in an arbitrary sub-directory

  • **/node_modules/** — Matches any file or folder in an arbitrary sub-directory of a node_modules folder, which can itself be in an arbitrary sub-directory of the public directory

  • **/*.@(jpg|jpeg|gif|png) — Matches any file in an arbitrary sub-directory that ends with exactly one of the following: .jpg, .jpeg, .gif, or .png

Full Hosting configuration example

The following is a full firebase.json configuration example for Firebase Hosting. Note that a firebase.json file can also contain configurations for other Firebase services.

{
  "hosting": {

    "public": "dist/app",  // "public" is the only required attribute for Hosting

    "ignore": [
      "firebase.json",
      "**/.*",
      "**/node_modules/**"
    ],

    "redirects": [ {
      "source": "/foo",
      "destination": "/bar",
      "type": 301
    }, {
      "source": "/firebase/**",
      "destination": "https://www.firebase.com",
      "type": 302
    } ],

    "rewrites": [ {
      // Shows the same content for multiple URLs
      "source": "/app/**",
      "destination": "/app/index.html"
    }, {
      // Configures a custom domain for Dynamic Links
      "source": "/promos/**",
      "dynamicLinks": true
    }, {
      // Directs a request to Cloud Functions
      "source": "/bigben",
      "function": "bigben"
    }, {
      // Directs a request to a Cloud Run containerized app
      "source": "/helloworld",
      "run": {
        "serviceId": "helloworld",
        "region": "us-central1"
      }
    } ],

    "headers": [ {
      "source": "**/*.@(eot|otf|ttf|ttc|woff|font.css)",
      "headers": [ {
        "key": "Access-Control-Allow-Origin",
        "value": "*"
      } ]
    }, {
      "source": "**/*.@(jpg|jpeg|gif|png)",
      "headers": [ {
        "key": "Cache-Control",
        "value": "max-age=7200"
      } ]
    }, {
      "source": "404.html",
      "headers": [ {
        "key": "Cache-Control",
        "value": "max-age=300"
      } ]
    } ],

    "cleanUrls": true,

    "trailingSlash": false,

    // Required to configure custom domains for Dynamic Links
    "appAssociation": "AUTO",

  }
}