Introduction

Configuration Reference

This page is a reference to the different ways of configuring your Vercel projects and Vercel CLI.

Using a vercel.json configuration file, placed at the root of a project, you can provide a list of options that changes the default behavior of the Vercel platform.

Configuration options for the following are described on this page:

Project

functions

Type: Object of key String and value Object.

Key definition:

A glob pattern that matches the paths of the Serverless Functions you would like to customize (like api/*.js or api/test.js).

Value definition:

• runtime (optional): The npm package name of a Runtime, including its version.
• memory (optional): An integer defining the memory your Serverless Function should be provided with (between 128 and 3008, in intervals of 64).
• maxDuration (optional): An integer defining how long your Serverless Function should be allowed to run on every request in seconds (between 1 and the maximum limit of your plan, as mentioned below).
• includeFiles (optional): A glob pattern to match files that should be included in your Serverless Function. If you’re using a Community Runtime, the behavior might vary. Please consult its documentation for more details.
• excludeFiles (optional): A glob pattern to match files that should be excluded from your Serverless Function. If you’re using a Community Runtime, the behavior might vary. Please consult its documentation for more details.

Description:

By default, no configuration is needed to deploy Serverless Functions to Vercel.

For all officially supported runtimes, the only requirement is to create an api directory at the root of your project directory, placing your Serverless Functions inside.

When deployed, each Serverless Function receives the following properties:

• Memory: 1024 MB (1 GB)
• Maximum Execution Duration: 10s (Hobby), 60s (Pro), or 900s (Enterprise)

To configure them, you can add the functions property like so:

{
  "functions": {
    "api/test.js": {
      "memory": 3008,
      "maxDuration": 60
    }
  }
}

Both sub properties are optional and need to match the following constraints mentioned at the top of this section.

In order to use a runtime that is not officially supported, you can add a runtime property to the definition:

{
  "functions": {
    "api/test.php": {
      "runtime": "vercel-php@0.1.0"
    }
  }
}

In the example above, the api/test.php Serverless Function does not use one of the officially supported runtimes. In turn, a runtime property was added in order to invoke the vercel-php community runtime.

For more information on Runtimes, see the documentation:

regions

Type: Array of region identifier String.

Valid values: a list of valid region identifiers.

By setting and modifying this value, you can decide the deployment regions of the Serverless Functions that get created as a result of the build steps. The region iad1 is used by default.

This value does not impact static files or edge caches, since deployments always have a CDN layer in front.

The special value all can be used to target all available regions.

{
  "regions": ["iad1", "sfo"]
}

public

Type: Boolean.

Default Value: false.

When set to true, both the source view and logs view will be publicly accessible.

{
  "public": true
}

cleanUrls

Type: Boolean.

Default Value: false.

When set to true, all HTML files and Serverless Functions will have their extension removed. When visiting a path that ends with the extension, a 308 response will redirect the client to the extensionless path.

For example, a static file named about.html will be served when visiting the /about path. Visiting /about.html will redirect to /about.

Similarly, a Serverless Function named api/user.go will be served when visiting /api/user. Visiting /api/user.go will redirect to /api/user.

{
  "cleanUrls": true
}

trailingSlash

Type: Boolean.

Default Value: undefined.

false

When trailingSlash: false, visiting a path that ends with a forward slash will respond with a 308 status code and redirect to the path without the trailing slash.

For example, the /about/ path will redirect to /about.

{
  "trailingSlash": false
}

true

When trailingSlash: true, visiting a path that does not end with a forward slash will respond with a 308 status code and redirect to the path with a trailing slash.

For example, the /about path will redirect to /about/.

However, paths with a file extension will not redirect to a trailing slash.

For example, the /about/styles.css path will not redirect, but the /about/styles path will redirect to /about/styles/.

{
  "trailingSlash": true
}

undefined

When trailingSlash: undefined, visiting a path with or without a trailing slash will not redirect.

For example, both /about and /about/ will serve the same content without redirecting.

This is not recommended because it could lead to search engines indexing two different pages with duplicate content.

redirects

Type: Array of redirect Object.

Valid values: a list of redirect definitions.

Limits:

• A maximum of 1,024 redirects in the array.
• A maximum of string length of 4,096 for the source and destination values.

Redirect object definition:

• source: A pattern that matches each incoming pathname (excluding querystring).
• destination: A location destination defined as an absolute pathname or external URL.
• permanent: A boolean to toggle between permanent and temporary redirect (default true). When true, the status code is 308. When false the status code is 307.

This example configures custom redirects that map to static files, Serverless Functions, and external URLs.

{
  "redirects": [
    { "source": "/me", "destination": "/profile.html" },
    { "source": "/user", "destination": "/api/user", "permanent": false },
    { "source": "/view-source", "destination": "https://github.com/vercel/vercel" }
  ]
}

In some rare cases, you might need to assign a custom status code for older HTTP Clients to properly redirect. In these cases, you can use the statusCode property instead of the permanent property, but not both.

rewrites

Type: Array of rewrite Object.

Valid values: a list of rewrite definitions.

Limits:

• A maximum of 1,024 rewrites in the array.
• A maximum of string length of 4,096 for the source and destination values.

Rewrite object definition:

• source: A pattern that matches each incoming pathname (excluding querystring).
• destination: An absolute pathname to an existing resource or an external URL.

This example configures custom rewrites that map to static files, Serverless Functions, automatic query string matching, and a wildcard proxy.

{
  "rewrites": [
    { "source": "/about", "destination": "/about-our-company.html" },
    { "source": "/resize/:width/:height", "destination": "/api/sharp" },
    { "source": "/user/:id", "destination": "/api/user" },
    { "source": "/proxy/:match*", "destination": "https://example.com/:match*" }
  ]
}

headers

Type: Array of header Object.

Valid values: a list of header definitions.

Limits:

• A maximum of 1,024 headers in the array.
• A maximum of string length of 4,096 for the source, key, and value values.

Header object definition:

• source: A pattern that matches each incoming pathname (excluding querystring).
• headers: An array of key/value pairs representing each response header.

This example configures custom response headers for static files, Serverless Functions, and a wildcard that matches all routes.

{
  "headers": [
    {
      "source": "/service-worker.js",
      "headers" : [
        {
          "key" : "Cache-Control",
          "value" : "public, max-age=0, must-revalidate"
        }
      ]
    },
    {
      "source": "/api/feed",
      "headers" : [
        {
          "key" : "Content-Type",
          "value" : "application/rss+xml"
        },
        {
          "key" : "Cache-Control",
          "value" : "public, max-age=3600"
        }
      ]
    },
    {
      "source": "/(.*)",
      "headers" : [
        {
          "key" : "X-Content-Type-Options",
          "value" : "nosniff"
        },
        {
          "key" : "X-Frame-Options",
          "value" : "DENY"
        },
        {
          "key" : "X-XSS-Protection",
          "value" : "1; mode=block"
        }
      ]
    }
  ]
}

name

Type: String.

Valid values: string name for the deployment.

Limits:

• A maximum length of 52 characters
• Only lower case alphanumeric characters or hyphens are allowed
• Cannot begin or end with a hyphen, or contain multiple consecutive hyphens

The prefix for all new deployment instances. The CLI usually generates this field automatically based on the name of the directory. But if you'd like to define it explicitly, this is the way to go.

The defined name is also used to organize the deployment into a project.

{
  "name": "example-app"
}

version

Type: Number.

Valid values: 1, 2.

Specifies the Vercel Platform version the deployment should use.

{
  "version": 2
}

alias

Type: Array or String.

Valid values: domain names (optionally including subdomains) added to the account, or a string for a suffixed URL using .vercel.app or a Custom Deployment Suffix (available on the Enterprise plan).

Limit: A maximum of 64 aliases in the array.

The alias or aliases are applied automatically using Vercel for GitHub, Vercel for GitLab, or Vercel for Bitbucket when merging or pushing to the Production Branch.

You can deploy to the defined aliases using Vercel CLI by setting the production deployment environment target.

{
  "alias": ["my-domain.com", "my-alias"]
}

scope

Type: String.

Valid values: For teams, either an ID or slug. For users, either a email address, username, or ID.

This property determines the scope (user or team) under which the project will be deployed by Vercel CLI.

Furthermore, it also affects any other actions that the user takes within the directory that contains this configuration (e.g. listing Environment Variables using vercel secrets ls).

{
  "scope": "my-team"
}

env

Type: Object of String keys and values.

Valid values: environment keys and values.

Environment variables passed to the invoked Serverless Functions.

This example will pass the MY_KEY static env to all Serverless Functions and SECRET resolved from the my-secret-name Secret dynamically.

{
  "env": {
    "MY_KEY": "this is the value",
    "SECRET": "@my-secret-name"
  }
}

build.env

Type: Object of String keys and values inside the build Object.

Valid values: environment keys and values.

Environment variables passed to the Build processes.

The following example will pass the MY_KEY Environment Variable to all Builds and SECRET resolved from the my-secret-name Secret dynamically.

{
  "build": {
    "env": {
      "MY_KEY": "this is the value",
      "SECRET": "@my-secret-name"
    }
  }
}

builds

Type: Array of build Object.

Valid values: a list of build descriptions whose src references valid source files.

Build object definition:

• src (String): A glob expression or pathname. If more than one file is resolved, one build will be created per matched file. It can include * and **.
• use (String): An npm module to be installed by the build process. It can include a semver compatible version (e.g.: @org/proj@1).
• config (Object): Optionally, an object including arbitrary metadata to be passed to the Builder.

The following will include all HTML files as-is (to be served statically), and build all Python files and JS files into Serverless Functions.

{
  "builds": [
    { "src": "*.html", "use": "@vercel/static" },
    { "src": "*.py", "use": "@vercel/python" },
    { "src": "*.js", "use": "@vercel/node" }
  ]
}

routes

Type: Array of route Object.

Valid values: a list of route definitions.

Route object definition:

• src: A PCRE-compatible regular expression that matches each incoming pathname (excluding querystring).
• methods: A set of HTTP method types. If no method is provided, requests with any HTTP method will be a candidate for the route.
• dest: A destination pathname or full URL, including querystring, with the ability to embed capture groups as $1, $2…
• headers: A set of headers to apply for responses.
• status: A status code to respond with. Can be used in tandem with Location: header to implement redirects.
• continue: A boolean to change matching behavior. If true, routing will continue even when the src is matched.

Routes are processed in the order they are defined in the array, so wildcard/catch-all patterns should usually be last.

This example configures custom routes that map to static files and Serverless Functions.

{
  "routes": [
    { "src": "/redirect", "status": 308, "headers": { "Location": "https://example.com/" } },
    { "src": "/custom-page", "headers": {"cache-control": "s-maxage=1000"}, "dest": "/index.html" },
    { "src": "/api", "dest": "/my-api.js" },
    { "src": "/users", "methods": ["POST"], "dest": "/users-api.js" },
    { "src": "/users/(?<id>[^/]*)", "dest": "/users-api.js?id=$id" },
    { "src": "/legacy", "status": 404},
    { "src": "/.*", "dest": "https://my-old-site.com"}
  ]
}

Upgrading

In most cases, you can upgrade legacy routes usage to the newer rewrites, redirects, headers, cleanUrls or trailingSlash properties.

Here are some examples that show how to upgrade legacy routes to the equivalent new property.

Route Parameters

With routes, you use a PCRE Regex named group to match the ID and then pass that parameter in the query string.

{
  "routes": [{ "src": "/product/(?<id>[^/]+)", "dest": "/api/product?id=$id" }]
}

Match URL like /product/532004 and proxy to /api/product?id=532004.

With rewrites, named parameters are automatically passed in the query string.

{
  "rewrites": [{ "source": "/product/:id", "destination": "/api/product" }]
}

Equivalent to the legacy routes usage above, but instead using rewrites.

Redirects

With routes, you specify the status code to use a 307 Temporary Redirect. Also, this redirect needs to be defined before other routes.

{
  "routes": [
    {
      "src": "/posts/(.*)",
      "headers": { "Location": "/blog/$1" },
      "status": 307
    }
  ]
}

Redirecting from all paths in the posts directory but keeping the path in the new location.

With redirects, you disable the permanent property to use a 307 Temporary Redirect. Also, redirects are always processed before rewrites.

{
  "redirects": [
    {
      "source": "/posts/:id",
      "destination": "/blog/:id",
      "permanent": false
    }
  ]
}

Equivalent to the legacy routes usage above, but instead using redirects.

SPA Fallback

With routes, you use "handle": "filesystem" to give precedence to the filesytem and exit early if the requested path matched a file.

{
  "routes": [
    { "handle": "filesystem" },
    { "src": "/(.*)", "dest": "/index.html" }
  ]
}

Fallback to index.html after checking the filesystem for exact matches.

With rewrites, the filesystem check is the default behavior. If you want to change the name of files at the filesystem level, file renames can be performed during the Build Step, but not with rewrites.

{
  "rewrites": [{ "source": "/(.*)", "destination": "/index.html" }]
}

Equivalent to the legacy routes usage above, but instead using rewrites.

Headers

With routes, you use "continue": true to prevent stopping at the first match.

{
  "routes": [
    {
      "src": "/favicon.ico",
      "headers": { "Cache-Control": "public, max-age=3600" },
      "continue": true
    },
    {
      "src": "/assets/(.*)",
      "headers": { "Cache-Control": "public, max-age=31556952, immutable" },
      "continue": true
    }
  ]
}

Add Cache-Control headers to favicon and other static assets.

With headers, this is no longer necessary since that is the default behavior.

{
  "headers": [
    {
      "source": "/favicon.ico",
      "headers": [
        {
          "key": "Cache-Control",
          "value": "public, max-age=3600"
        }
      ]
    },
    {
      "source": "/assets/(.*)",
      "headers": [
        {
          "key": "Cache-Control",
          "value": "public, max-age=31556952, immutable"
        }
      ]
    }
  ]
}

Equivalent to the legacy routes usage above, but instead using headers.

Pattern Matching

With routes, you need to escape a dot with two backslashes, otherwise it would match any character PCRE Regex.

{
  "routes": [{ "src": "/atom\\.xml", "dest": "/api/rss" }]
}

Match the literal /atom.xml and proxy to /api/rss to dynamically generate RSS.

With rewrites, the . is not a special character so it does not need to be escaped.

{
  "rewrites": [{ "source": "/atom.xml", "destination": "/api/rss" }]
}

Equivalent to the legacy routes usage above, but instead using rewrites.

Negative Lookahead

With routes, you use PCRE Regex negative lookahead.

{
  "routes": [{ "src": "/(?!maintenance)", "dest": "/maintenance" }]
}

Proxy all requests to the /maintenance except for /maintenance directly to avoid infinite loop.

With rewrites, the Regex needs to be wrapped.

{
  "rewrites": [
    { "source": "/((?!maintenance).*)", "destination": "/maintenance" }
  ]
}

Equivalent to the legacy routes usage above, but instead using rewrites.

Case Sensitivity

With routes, the src property is case-insensitive leading to duplicate content, where multiple request paths with difference cases serve the same page.

With rewrites / redirects / headers, the source property is case-sensitive so you don't accidentally create duplicate content.

Git

The following configuration options can be used through a vercel.json file like the options above.

github.enabled

Type: Boolean.

When set to false, Vercel for GitHub will not deploy the given project regardless of the GitHub app being installed.

{
  "github": {
    "enabled": false
  }
}

github.autoAlias

Type: Boolean.

When set to false, Vercel for GitHub will not apply the alias upon merge.

{
  "alias": ["example.com"],
  "github": {
    "autoAlias": false
  }
}

github.silent

Type: Boolean.

When set to true, Vercel for GitHub will stop commenting on pull requests and commits.

{
  "github": {
    "silent": true
  }
}

github.autoJobCancelation

Type: Boolean.

When set to false, Vercel for GitHub will always build pushes in sequence without cancelling a build for the most recent commit.

{
  "github": {
    "autoJobCancelation": false
  }
}

Global

Using the following files and configuration options, you can configure Vercel CLI under your system user.

There are two global configuration files; config.json and auth.json. By default, these files are held in a directory named .vercel within the user's home directory. For example on Unix based systems they will be found at ~/.vercel/*.json.

config.json

This file is used for global configuration of Vercel deployments. Vercel CLI uses this file as a way to co-ordinate how deployments should be treated, consistently.

The first option is a single _ that gives a description to the file, if a user should find themselves looking through it without context.

The following options are all of the options that can be used by users to configure their Vercel deployments globally on their system for that user profile:

currentTeam

Type: String.

Valid values: A team ID.

This option tells Vercel CLI which context is currently active. If this property exists and contains a team ID, that team is used as the scope for deployments, otherwise if this property does not exist, the user's personal account is used.

{
  "currentTeam": "team_ofwUZockJlL53hINUGCc1ONW"
}

api

Type: String.

Valid values: An API Origin URL.

This option selects which API Origin Vercel CLI should use when performing an action requiring the API.

{
  "api": "https://api-sfo1.zeit.co"
}

collectMetrics

Type: Boolean.

Valid values: true (default), false.

This option defines whether Vercel CLI should collect anonymous metrics about which commands are invoked the most, how long they take to run, and which errors customers are running into.

{
  "collectMetrics": true
}

auth.json

This file should not be edited manually. It exists to contain the authentication information for the Vercel clients.

In the case that you are uploading your global configuration setup to a potentially insecure destination, we highly recommend ensuring that this file will not be uploaded, as it allows an attacker to gain access to your provider accounts.