# How to add website leads to Mailchimp (with consent)

> Add customers who opt in to your Mailchimp audience with the API, without resubscribing people who left. Your API key, data centre and audience ID.

Source: https://roughfigure.com/blog/add-website-leads-to-mailchimp (updated 2026-11-11)

To add website leads to Mailchimp, create an **API key** (it ends with your data centre, like `-us21`), copy your **Audience ID**, and add each person to `/lists/{audience_id}/members` on `https://<dc>.api.mailchimp.com/3.0`. Only add people who ticked a box agreeing to hear from you, and don’t resubscribe anyone who unsubscribed before.

## Who should go into Mailchimp

A customer asking for a fencing price has agreed to hear about their fence. They haven’t agreed to your spring offers. Put a separate, unticked box on your form (“Send me occasional tips and offers”) and only send those who tick it to Mailchimp. Everyone else belongs in your CRM or lead list. [Consent for CRM and newsletter leads](https://roughfigure.com/blog/consent-for-crm-and-newsletter-leads) covers the rules.

## Find your key and audience ID

1. Profile icon → **Account & billing → Extras → API keys** → **Create a key**. The part after the dash is your data centre.
2. **Audience → Settings → Audience name and defaults** shows the **Audience ID**.

## Add the subscriber

```http
POST https://us21.api.mailchimp.com/3.0/lists/<audience_id>/members
Authorization: Bearer <your API key>
Content-Type: application/json

{
  "email_address": "daniel.price@mail.test",
  "status": "subscribed",
  "merge_fields": { "FNAME": "Daniel", "LNAME": "Price" },
  "tags": ["website-estimator"]
}
```

If the person is already in your audience, Mailchimp replies **400 “Member Exists”**. That’s good: it means you haven’t changed the status of someone who might have unsubscribed. Treat it as done.

## Why not PUT (add or update)?

`PUT /lists/{id}/members/{hash}` with `status_if_new` adds or updates in one call, and is handy for updating names. But if you send `status: subscribed` on an update, you can resubscribe someone who left, which breaks the law in many countries and Mailchimp’s rules. Use `status_if_new` only, and leave `status` out.

## Single or double opt-in?

`subscribed` adds them straight away. `pending` sends a confirmation email first. Double opt-in gives you a cleaner list and stronger proof of consent; single opt-in loses fewer people. Either is fine with a clear, unticked box.

## Doing it in RoughFigure

In RoughFigure we’ve built Mailchimp in as one of nine direct newsletter connections. Under **Integrations → Add leads to your newsletter**, choose **Mailchimp**, paste your API key and Audience ID, and click **Connect**. Only customers who ticked your marketing box and then confirmed by email are added, with their name. We send that confirmation ourselves, so leave Mailchimp’s own double opt-in off, and anyone who unsubscribed before is left alone. [See the Mailchimp integration](https://roughfigure.com/integrations/mailchimp), or [all integrations](https://roughfigure.com/integrations).

## Questions

### Why does my API key stop working after a while?

Keys are revoked if someone deletes them, or if Mailchimp spots one exposed in public code. Create a new one and update it wherever it’s used.

### Can I add a tag to people who came from my website?

Yes. Add `tags` to the request, as above. Tags are free to use and don’t count as separate audiences.

### Do contacts who don’t opt in count towards my Mailchimp bill?

Only if you add them. Keeping non-subscribers out of Mailchimp keeps your list, and your bill, smaller.