Paul Laros

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How to get the current URL with Next.js on Vercel ​

Vercel, a popular platform for deploying Next.js applications, provides convenient ways to manage environment variables. One such variable, NEXT_PUBLIC_VERCEL_URL, can be particularly useful for obtaining the current URL of your application. In scenarios where dynamic preview URLs are generated on Vercel, obtaining the current URL can be challenging. In this article, we'll explore how to obtain dynamic URLs and leverage the dotenv-expand package, in a Next.js project.

Exposing Environment Variables ​

Vercel simplifies the process of exposing system environment variables to your deployments. By checking the Automatically expose System Environment Variables checkbox in your deployment settings, Vercel automatically exposes variables like NEXT_PUBLIC_VERCEL_URL to your application.

Environment Variable Setup ​

Managing URLs across different environments is a common requirement in web development. Here's how you can set up environment variables for different environments in your Next.js project.

Development Environment ​

In your development environment, you can define the NEXT_PUBLIC_URL variable in your .env.development file:

plaintext
NEXT_PUBLIC_URL=http://localhost:3000

Production Environment ​

For the production environment, you can utilize the NEXT_PUBLIC_VERCEL_URL variable provided by Vercel. This can be set in your .env.production file or directly in the Environment Variables settings of your Vercel project:

plaintext
NEXT_PUBLIC_URL=https://$NEXT_PUBLIC_VERCEL_URL

Handling Environment Variables ​

A common issue with directly using NEXT_PUBLIC_URL=https://$NEXT_PUBLIC_VERCEL_URL in your environment varariables file is that it outputs a literal string in your application when using process.env.NEXT_PUBLIC_URL, which may not be desirable. To work around this limitation and ensure dynamic variable handling, consider using the dotenv-expand package.

Installation ​

You can install the dotenv-expand package via npm:

sh
npm install dotenv-expand

Integration with Next.js ​

After installing dotenv-expand, integrate it into your Next.js configuration file:

javascript
// next.config.js

const dotenvExpand = require("dotenv-expand");

dotenvExpand.expand({ parsed: { ...process.env } });

// The rest of your config

By adding dotenv-expand into your project, the environment variable value will be dynamically expanded, providing a more flexible approach to handling URLs in your Next.js application.

How to use ​

By making this change, you're able to access the current URL of your application in your development environment, preview environments, and production environment, ensuring seamless functionality across all stages of development.

js
console.log(process.env.NEXT_PUBLIC_URL);

// Output localhost: http://localhost:3000
// Output preview: https://random-url.vercel.app
// Output production: https://your-website.com