Rewrites

Rewrites allow you to map an incoming request path to a different destination path.

Rewrites are only available on the Node.js environment and do not affect client-side routing.

To use rewrites you can use the rewrites key in blitz.config.js:

module.exports = {
  async rewrites() {
    return [
      {
        source: "/about",
        destination: "/",
      },
    ]
  },
}

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

source: String - is the incoming request path pattern.
destination: String is the path you want to route to.
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.

Rewrites are applied after checking the filesystem (pages and /public files) and before dynamic routes by default.

module.exports = {
  async rewrites() {
    return {
      beforeFiles: [
        // These rewrites are checked after headers/redirects
        // and before pages/public files which allows overriding
        // page files
        {
          source: "/some-page",
          destination: "/somewhere-else",
          has: [{ type: "query", key: "overrideMe" }],
        },
      ],
      afterFiles: [
        // These rewrites are checked after pages/public files
        // are checked but before dynamic routes
        {
          source: "/non-existent",
          destination: "/somewhere-else",
        },
      ],
      fallback: [
        // These rewrites are checked after both pages/public files
        // and dynamic routes are checked
        {
          source: "/:path*",
          destination: `https://my-old-site.com/:path*`,
        },
      ],
    }
  },
}

Note: rewrites in beforeFiles do not check the filesystem/dynamic routes immediately after matching a source, they continue until all beforeFiles have been checked.

The order Blitz.js routes are checked is:

headers are checked/applied
redirects are checked/applied
beforeFiles rewrites are checked/applied
static files from the public directory, _next/static files, and non-dynamic pages are checked/served
afterFiles rewrites are checked/applied, if one of these rewrites is matched we check dynamic routes/static files after each match
fallback rewrites are checked/applied, these are applied before rendering the 404 page and after dynamic routes/all static assets have been checked.

Rewrite parameters

When using parameters in a rewrite the parameters will be passed in the query by default when none of the parameters are used in the destination.

module.exports = {
  async rewrites() {
    return [
      {
        source: "/old-about/:path*",
        destination: "/about", // The :path parameter isn't used here so will be automatically passed in the query
      },
    ]
  },
}

If a parameter is used in the destination none of the parameters will be automatically passed in the query.

module.exports = {
  async rewrites() {
    return [
      {
        source: "/docs/:path*",
        destination: "/:path*", // The :path parameter is used here so will not be automatically passed in the query
      },
    ]
  },
}

You can still pass the parameters manually in the query if one is already used in the destination by specifying the query in the destination.

module.exports = {
  async rewrites() {
    return [
      {
        source: "/:first/:second",
        destination: "/:first?second=:second",
        // Since the :first parameter is used in the destination the :second parameter
        // will not automatically be added in the query although we can manually add it
        // as shown above
      },
    ]
  },
}

Path Matching

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

module.exports = {
  async rewrites() {
    return [
      {
        source: "/blog/:slug",
        destination: "/news/:slug", // Matched parameters can be used in the destination
      },
    ]
  },
}

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:

module.exports = {
  async rewrites() {
    return [
      {
        source: "/blog/:slug*",
        destination: "/news/:slug*", // Matched parameters can be used in the destination
      },
    ]
  },
}

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:

module.exports = {
  async rewrites() {
    return [
      {
        source: "/old-blog/:post(\\d{1,})",
        destination: "/blog/:post", // Matched parameters can be used in the destination
      },
    ]
  },
}

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:

module.exports = {
  async rewrites() {
    return [
      {
        // this will match `/english(default)/something` being requested
        source: "/english\\(default\\)/:slug",
        destination: "/en-us/:slug",
      },
    ]
  },
}

To only match a rewrite when header, cookie, or query values also match the has field can be used. Both the source and all has items must match for the rewrite to be applied.

has items 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.

module.exports = {
  async rewrites() {
    return [
      // if the header `x-rewrite-me` is present,
      // this rewrite will be applied
      {
        source: "/:path*",
        has: [
          {
            type: "header",
            key: "x-rewrite-me",
          },
        ],
        destination: "/another-page",
      },
      // if the source, query, and cookie are matched,
      // this rewrite will be applied
      {
        source: "/specific/:path*",
        has: [
          {
            type: "query",
            key: "page",
            // the page value will not be available in the
            // destination since value is provided and doesn't
            // use a named capture group e.g. (?<page>home)
            value: "home",
          },
          {
            type: "cookie",
            key: "authorized",
            value: "true",
          },
        ],
        destination: "/:path*/home",
      },
      // if the header `x-authorized` is present and
      // contains a matching value, this rewrite will be applied
      {
        source: "/:path*",
        has: [
          {
            type: "header",
            key: "x-authorized",
            value: "(?<authorized>yes|true)",
          },
        ],
        destination: "/home?authorized=:authorized",
      },
      // if the host is `example.com`,
      // this rewrite will be applied
      {
        source: "/:path*",
        has: [
          {
            type: "host",
            value: "example.com",
          },
        ],
        destination: "/another-page",
      },
    ]
  },
}

Rewriting to an external URL

Rewrites allow you to rewrite to an external url. This is especially useful for incrementally adopting Blitz.js

module.exports = {
  async rewrites() {
    return [
      {
        source: "/blog/:slug",
        destination: "https://example.com/blog/:slug", // Matched parameters can be used in the destination
      },
    ]
  },
}

Incremental adoption of Blitz.js

You can also have Blitz.js fall back to proxying to an existing website after checking all Blitz.js routes.

This way you don't have to change the rewrites configuration when migrating more pages to Blitz.js

module.exports = {
  async rewrites() {
    return {
      fallback: [
        {
          source: "/:path*",
          destination: `https://custom-routes-proxying-endpoint.vercel.app/:path*`,
        },
      ],
    }
  },
}

Rewrites with basePath support

When leveraging basePath support with rewrites each source and destination is automatically prefixed with the basePath unless you add basePath: false to the rewrite:

module.exports = {
  basePath: "/docs",

  async rewrites() {
    return [
      {
        source: "/with-basePath", // automatically becomes /docs/with-basePath
        destination: "/another", // automatically becomes /docs/another
      },
      {
        // does not add /docs to /without-basePath since basePath: false is set
        // Note: this can not be used for internal rewrites e.g. `destination: '/another'`
        source: "/without-basePath",
        destination: "https://example.com",
        basePath: false,
      },
    ]
  },
}

Rewrites with i18n support

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

module.exports = {
  i18n: {
    locales: ["en", "fr", "de"],
    defaultLocale: "en",
  },

  async rewrites() {
    return [
      {
        source: "/with-locale", // automatically handles all locales
        destination: "/another", // automatically passes the locale on
      },
      {
        // does not handle locales automatically since locale: false is set
        source: "/nl/with-locale-manual",
        destination: "/nl/another",
        locale: false,
      },
      {
        // this matches '/' since `en` is the defaultLocale
        source: "/en",
        destination: "/en/another",
        locale: false,
      },
      {
        // this gets converted to /(en|fr|de)/(.*) so will not match the top-level
        // `/` or `/fr` routes like /:path* would
        source: "/(.*)",
        destination: "/another",
      },
    ]
  },
}

Topics