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How can I increase the limit of redirects or use dynamic redirects on Vercel?

In this article, we describe methods to redirect a path to another location by using Next.js and Vercel features. Using Serverless Functions or Next.js pages to respond with a redirect is useful when you have dynamic redirects stored in a data source or if you reached the limit of redirects set in your next.config.js file or vercel.json.

With Next.js

If you are deploying a Next.js application to Vercel, you can define redirects in the following ways:

  1. Using the redirects configuration.
  2. Using a Next.js page.
  3. Using an API route.

Using redirects

The main characteristic of the redirects feature is that it is a build-time configuration. Which means it is only possible to generate it once before the application is deployed.

You can check the official Next.js documentation for instructions on how to define the redirects statically. At the moment, there is a limit of 1024 redirect rules that can be described in the configuration for Vercel deployed apps. If your application is near the 1024 limit, it is advised to check the official documentation for Regex Path Matching or alternative ways, as described below.

// next.config.js
module.exports = {
  async redirects() {
    return [
      {
        source: "/legacy/:path*",
        destination: "/new/:path"
      }
    ]
  }
}

Redirect configuration that redirects /legacy/abc123example to /new/abc123example.

Using a Next.js Page

Performing redirects using a Next.js page gives your deployment the ability to fallback to a normal page with a presentable UI in case the redirect is not found. Therefore, using a page for redirects is recommended if you need to dynamically query an external resource to fetch your list of redirects, and those routes will be shared with your users. To avoid executing the Serverless Function for every request to a certain path, it is also recommended to cache the response.

// pages/redirects.js
import Error from 'next/error'

export async function getServerSideProps({req, res}) {
  // Insert redirect rules here
  if (req.url.startsWith('/example')) {
    res.statusCode = 308
    res.setHeader('location', '/test')
    // Caching headers
    res.setHeader('Cache-control', 's-maxage=600')
    return res.end()
  }
    
  return { props: { errorCode: 404 } }
}

export default function Page({ errorCode }) {
  return <div>`${errorCode}`</div>
}

Using a page to respond with a cacheable 308 redirect to /test.

Now that we have a page ready to accept requests and redirect given a condition, it is also necessary to route all relevant paths to the page above. In the code snippet below, we will use rewrites to adjust our routing behavior. 

// next.config.js
module.exports = {
  async rewrites() {
    return [
      {
        source: "/ad-campaign/:path*",
        destination: "/redirects"
      }
    ]
  }
}

Rewriting every path starting with /ad-campaign/ to /redirects.

Using an API Route

You can also perform redirects using an API Route. This method is recommended if you need to dynamically query an external resource to fetch your list of redirects, and you want an endpoint that can perform those redirects without a presentable page. To avoid invoking the Serverless Function for every request to a certain path, it is also recommended to cache the response.

// pages/api/redirects.js
export default (req, res) => {
  // Insert redirect rules here
  if (req.url.startsWith('/example')) {
    res.statusCode = 308
    res.setHeader('location', '/test')
    // Caching headers
    res.set('Cache-control', 's-maxage=600')
    return res.end()
  }

  res.statusCode = 404
  return res.end('Not found')
}

An API route that redirects a request programatically.

With the API route ready to accept requests and perform redirects, we need to configure the routing configuration of the Next.js deployment. In the code snippet below, we will use rewrites to adjust our routing behavior.

// next.config.js
module.exports = {
 async rewrites() {
   return [
     {
       source: "/ad-campaign/:path*",
       destination: "/api/redirects"
     }
   ]
 }
}

Rewriting every path starting with /ad-campaign/ to /api/redirects.

With Vercel.json

If you are not using Next.js, you can still define redirects in the following ways:

  1. Using the redirects configuration.
  2. Using a Serverless Function.

Using redirects with vercel.json

The redirects feature should be used if you need less than 1024 and you can describe them statically. If your application is near the 1024 limit, it is advised to check the official documentation for Regex Path Matching using a Serverless Function, as described in this article.

{
  "redirects": [
    {
      "source": "/legacy/:path*",
      "destination": "/new/:path*"
    }
  ]
}

Redirect configuration that redirects /legacy/abc123example to /new/abc123example.

Using a Serverless Function

You can perform redirects with a Serverless Function. This method is recommended if you need to dynamically query an external resource to fetch your list of redirects. To avoid invoking the Serverless Function for every request to a certain path, it is also recommended to cache the response.

// api/redirects.js
module.exports = async (req, res) => {
  // Insert redirect rules here
  if (req.url.startsWith('/example')) {
    res.statusCode = 308
    res.setHeader('location', '/test')
    // Caching headers
    res.set('Cache-control', 's-maxage=600')
    return res.end()
  }

  res.statusCode = 404
  return res.end('Not found')
}

An example of a Node.js Serverless Function to respond with a redirect.

We have created a Node.js Serverless Function that accepts requests and perform redirects programatically. The next step should be to create a new rewrite rule to adjust our routing behavior.

{
  "rewrites": [
    { "source": "/ad-campaign/:match*", "destination": "/api/redirects" }
  ]
}

Rewriting every path starting with /ad-campaign/ to /api/redirects.

Conclusion

As outlined in this article, there are multiple ways to perform redirects when deploying an application to Vercel. If you are using Next.js, it is recommended that you use the next.config.js configuration if you need statically defined rewrites. If you need to query external resources or perform server-side computation, using a Next.js page or an API Route gives you the required flexibility for advanced use-cases. For other frameworks, you can either define statically your redirects with vercel.json or use Serverless Functions for advanced requirements.

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