headers

Headers allow you to set custom HTTP headers on the response to an incoming request on a given path.

To set custom HTTP headers you can use the headers key in next.config.js:

next.config.js

module.exports = {
  async headers() {
    return [
      {
        source: '/about',
        headers: [
          {
            key: 'x-custom-header',
            value: 'my custom header value',
          },
          {
            key: 'x-another-custom-header',
            value: 'my other custom header value',
          },
        ],
      },
    ];
  },
};

headers is an async function that expects an array to be returned holding objects with source and headers properties:

source is the incoming request path pattern.
headers is an array of response header objects, with key and value properties.
basePath: false or undefined - if false the basePath won't be included when matching, can be used for external rewrites only.
locale: false or undefined - whether the locale should not be included when matching.
has is an array of has objects with the type, key and value properties.
missing is an array of missing objects with the type, key and value properties.

Headers are checked before the filesystem which includes pages and /public files.

Header Overriding Behavior

If two headers match the same path and set the same header key, the last header key will override the first. Using the below headers, the path /hello will result in the header x-hello being world due to the last header value set being world.

next.config.js

module.exports = {
  async headers() {
    return [
      {
        source: '/:path*',
        headers: [
          {
            key: 'x-hello',
            value: 'there',
          },
        ],
      },
      {
        source: '/hello',
        headers: [
          {
            key: 'x-hello',
            value: 'world',
          },
        ],
      },
    ];
  },
};

Path Matching

Path matches are allowed, for example /blog/:slug will match /blog/hello-world (no nested paths):

next.config.js

module.exports = {
  async headers() {
    return [
      {
        source: '/blog/:slug',
        headers: [
          {
            key: 'x-slug',
            value: ':slug', // Matched parameters can be used in the value
          },
          {
            key: 'x-slug-:slug', // Matched parameters can be used in the key
            value: 'my other custom header value',
          },
        ],
      },
    ];
  },
};

Wildcard Path Matching

To match a wildcard path you can use * after a parameter, for example /blog/:slug* will match /blog/a/b/c/d/hello-world:

next.config.js

module.exports = {
  async headers() {
    return [
      {
        source: '/blog/:slug*',
        headers: [
          {
            key: 'x-slug',
            value: ':slug*', // Matched parameters can be used in the value
          },
          {
            key: 'x-slug-:slug*', // Matched parameters can be used in the key
            value: 'my other custom header value',
          },
        ],
      },
    ];
  },
};

Regex Path Matching

To match a regex path you can wrap the regex in parenthesis after a parameter, for example /blog/:slug(\\d{1,}) will match /blog/123 but not /blog/abc:

next.config.js

module.exports = {
  async headers() {
    return [
      {
        source: '/blog/:post(\\d{1,})',
        headers: [
          {
            key: 'x-post',
            value: ':post',
          },
        ],
      },
    ];
  },
};

The following characters (, ), {, }, :, *, +, ? are used for regex path matching, so when used in the source as non-special values they must be escaped by adding \\ before them:

next.config.js

module.exports = {
  async headers() {
    return [
      {
        // this will match `/english(default)/something` being requested
        source: '/english\\(default\\)/:slug',
        headers: [
          {
            key: 'x-header',
            value: 'value',
          },
        ],
      },
    ];
  },
};

To only apply a header when header, cookie, or query values also match the has field or don't match the missing field can be used. Both the source and all has items must match and all missing items must not match for the header to be applied.

has and missing items can have the following fields:

type: String - must be either header, cookie, host, or query.
key: String - the key from the selected type to match against.
value: String or undefined - the value to check for, if undefined any value will match. A regex like string can be used to capture a specific part of the value, e.g. if the value first-(?<paramName>.*) is used for first-second then second will be usable in the destination with :paramName.

next.config.js

module.exports = {
  async headers() {
    return [
      // if the header `x-add-header` is present,
      // the `x-another-header` header will be applied
      {
        source: '/:path*',
        has: [
          {
            type: 'header',
            key: 'x-add-header',
          },
        ],
        headers: [
          {
            key: 'x-another-header',
            value: 'hello',
          },
        ],
      },
      // if the header `x-no-header` is not present,
      // the `x-another-header` header will be applied
      {
        source: '/:path*',
        missing: [
          {
            type: 'header',
            key: 'x-no-header',
          },
        ],
        headers: [
          {
            key: 'x-another-header',
            value: 'hello',
          },
        ],
      },
      // if the source, query, and cookie are matched,
      // the `x-authorized` header will be applied
      {
        source: '/specific/:path*',
        has: [
          {
            type: 'query',
            key: 'page',
            // the page value will not be available in the
            // header key/values since value is provided and
            // doesn't use a named capture group e.g. (?<page>home)
            value: 'home',
          },
          {
            type: 'cookie',
            key: 'authorized',
            value: 'true',
          },
        ],
        headers: [
          {
            key: 'x-authorized',
            value: ':authorized',
          },
        ],
      },
      // if the header `x-authorized` is present and
      // contains a matching value, the `x-another-header` will be applied
      {
        source: '/:path*',
        has: [
          {
            type: 'header',
            key: 'x-authorized',
            value: '(?<authorized>yes|true)',
          },
        ],
        headers: [
          {
            key: 'x-another-header',
            value: ':authorized',
          },
        ],
      },
      // if the host is `example.com`,
      // this header will be applied
      {
        source: '/:path*',
        has: [
          {
            type: 'host',
            value: 'example.com',
          },
        ],
        headers: [
          {
            key: 'x-another-header',
            value: ':authorized',
          },
        ],
      },
    ];
  },
};

Headers with basePath support

When leveraging basePath support with headers each source is automatically prefixed with the basePath unless you add basePath: false to the header:

next.config.js

module.exports = {
  basePath: '/docs',
 
  async headers() {
    return [
      {
        source: '/with-basePath', // becomes /docs/with-basePath
        headers: [
          {
            key: 'x-hello',
            value: 'world',
          },
        ],
      },
      {
        source: '/without-basePath', // is not modified since basePath: false is set
        headers: [
          {
            key: 'x-hello',
            value: 'world',
          },
        ],
        basePath: false,
      },
    ];
  },
};

Headers with i18n support

When leveraging i18n support with headers each source is automatically prefixed to handle the configured locales unless you add locale: false to the header. If locale: false is used you must prefix the source with a locale for it to be matched correctly.

next.config.js

module.exports = {
  i18n: {
    locales: ['en', 'fr', 'de'],
    defaultLocale: 'en',
  },
 
  async headers() {
    return [
      {
        source: '/with-locale', // automatically handles all locales
        headers: [
          {
            key: 'x-hello',
            value: 'world',
          },
        ],
      },
      {
        // does not handle locales automatically since locale: false is set
        source: '/nl/with-locale-manual',
        locale: false,
        headers: [
          {
            key: 'x-hello',
            value: 'world',
          },
        ],
      },
      {
        // this matches '/' since `en` is the defaultLocale
        source: '/en',
        locale: false,
        headers: [
          {
            key: 'x-hello',
            value: 'world',
          },
        ],
      },
      {
        // this gets converted to /(en|fr|de)/(.*) so will not match the top-level
        // `/` or `/fr` routes like /:path* would
        source: '/(.*)',
        headers: [
          {
            key: 'x-hello',
            value: 'world',
          },
        ],
      },
    ];
  },
};

Cache-Control

You can set the Cache-Control header in your Next.js API Routes by using the res.setHeader method:

pages/api/user.js

export default function handler(req, res) {
  res.setHeader('Cache-Control', 's-maxage=86400');
  res.status(200).json({ name: 'John Doe' });
}

You cannot set Cache-Control headers in next.config.js file as these will be overwritten in production to ensure that API Routes and static assets are cached effectively.

If you need to revalidate the cache of a page that has been statically generated, you can do so by setting the revalidate prop in the page's getStaticProps function.

Options

X-DNS-Prefetch-Control

This header controls DNS prefetching, allowing browsers to proactively perform domain name resolution on external links, images, CSS, JavaScript, and more. This prefetching is performed in the background, so the DNS is more likely to be resolved by the time the referenced items are needed. This reduces latency when the user clicks a link.

{
  key: 'X-DNS-Prefetch-Control',
  value: 'on'
}

Strict-Transport-Security

This header informs browsers it should only be accessed using HTTPS, instead of using HTTP. Using the configuration below, all present and future subdomains will use HTTPS for a max-age of 2 years. This blocks access to pages or subdomains that can only be served over HTTP.

If you're deploying to Vercel, this header is not necessary as it's automatically added to all deployments unless you declare headers in your next.config.js.

{
  key: 'Strict-Transport-Security',
  value: 'max-age=63072000; includeSubDomains; preload'
}

X-XSS-Protection

This header stops pages from loading when they detect reflected cross-site scripting (XSS) attacks. Although this protection is not necessary when sites implement a strong Content-Security-Policy disabling the use of inline JavaScript ('unsafe-inline'), it can still provide protection for older web browsers that don't support CSP.

{
  key: 'X-XSS-Protection',
  value: '1; mode=block'
}

X-Frame-Options

This header indicates whether the site should be allowed to be displayed within an iframe. This can prevent against clickjacking attacks. This header has been superseded by CSP's frame-ancestors option, which has better support in modern browsers.

{
  key: 'X-Frame-Options',
  value: 'SAMEORIGIN'
}

Permissions-Policy

This header allows you to control which features and APIs can be used in the browser. It was previously named Feature-Policy. You can view the full list of permission options here.

{
  key: 'Permissions-Policy',
  value: 'camera=(), microphone=(), geolocation=(), browsing-topics=()'
}

X-Content-Type-Options

This header prevents the browser from attempting to guess the type of content if the Content-Type header is not explicitly set. This can prevent XSS exploits for websites that allow users to upload and share files. For example, a user trying to download an image, but having it treated as a different Content-Type like an executable, which could be malicious. This header also applies to downloading browser extensions. The only valid value for this header is nosniff.

{
  key: 'X-Content-Type-Options',
  value: 'nosniff'
}

Referrer-Policy

This header controls how much information the browser includes when navigating from the current website (origin) to another. You can read about the different options here.

{
  key: 'Referrer-Policy',
  value: 'origin-when-cross-origin'
}

Content-Security-Policy

This header helps prevent cross-site scripting (XSS), clickjacking and other code injection attacks. Content Security Policy (CSP) can specify allowed origins for content including scripts, stylesheets, images, fonts, objects, media (audio, video), iframes, and more.

You can read about the many different CSP options here.

You can add Content Security Policy directives using a template string.

// Before defining your Security Headers
// add Content Security Policy directives using a template string.
 
const ContentSecurityPolicy = `
  default-src 'self';
  script-src 'self';
  child-src example.com;
  style-src 'self' example.com;
  font-src 'self';
`;

When a directive uses a keyword such as self, wrap it in single quotes ''.

In the header's value, replace the new line with a space.

{
  key: 'Content-Security-Policy',
  value: ContentSecurityPolicy.replace(/\s{2,}/g, ' ').trim()
}

Version History

Version	Changes
`v13.3.0`	`missing` added.
`v10.2.0`	`has` added.
`v9.5.0`	Headers added.