2024-12-11

When creating a new subscriber, Buttondown will now reject the request if a subscriber with the same email address already exists, even if that subscriber has unsubscribed or is otherwise in a "valid" state. We do this to protect the data and history of existing subscribers.

However, if you're looking for behavior more akin to an upsert, you can provide a X-Buttondown-Collision-Behavior header of overwrite or add in the request header:

curl -X POST https://api.buttondown.com/v1/subscribers \
  -H "X-Buttondown-Collision-Behavior: overwrite" \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"email_address": "john@example.com", "tags": ["newsletter-1", "newsletter-2"]}'

This is a slightly nuanced decision for you to make as an API caller; we've explained more about our default behavior and reasoning in the API endpoint docs.