Subscribe to a newsletter.

import fetch from 'isomorphic-unfetch';

export default async (req, res) => {
  const { email } = req.body;

  if (!email) {
    return res.status(400).json({ error: 'Email is required' });

  try {
    const LIST_ID = process.env.MAILCHIMP_LIST_ID;
    const API_KEY = process.env.MAILCHIMP_API_KEY;
    const DATACENTER = API_KEY.split('-')[1];

    const data = {
      email_address: email,
      status: 'subscribed'

    const response = await fetch(
        body: JSON.stringify(data),
        headers: {
          Authorization: `apikey ${API_KEY}`,
          'Content-Type': 'application/json'
        method: 'POST'

    if (response.status >= 400) {
      return res.status(400).json({
        error: `There was an error subscribing to the newsletter. Shoot me an email at [] and I'll add you to the list.`

    return res.status(201).json({ error: '' });
  } catch (error) {
    return res.status(500).json({ error: error.message || error.toString() });



Create Mailchimp Account

First, create a Mailchimp account. Then, generate an API key.


Find Audience ID

Each Mailchimp audience has a unique Audience ID. Retrieve the ID for the list you want to add a subscriber to.


Add Environment Variables

To securely access the API, we need to include the secret with each request. We also do not want to commit secrets to git. Thus, we should use an environment variable. Learn how to add environment variables in Vercel.

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