You don't need the next/env package in Next.js v15. It loads your env files automatically.

To know how to use environment variables in Next 15, you can check my article on using environment variables in next js, which describes the correct way to set up environment files and variables, and all the possible things that could go wrong including reasons why your variables could be undefined.

Some of the possible culprits are:

• not adding NEXT_PUBLIC_ in front of the variable when you need it in the client-side code
• not restarting your next server after adding the variables
• putting your env file in the wrong place
• not adding your variables in the dashboard when building on hosting platforms like Vercel or Netlify