Building a Plugin-Free Newsletter Popup on WordPress: Custom REST Endpoint Mailchimp API v3

219 · Vicente G. Reyes · July 7, 2026, 1:39 a.m.
Summary
This blog post details a custom implementation of a newsletter popup for WordPress without using plugins or external scripts. By leveraging a custom REST API endpoint, it maintains performance and brand control while integrating with Mailchimp. The author shares their architecture, code examples, anti-spam measures, and deployment notes, along with lessons learned during development, such as API key security and mobile design considerations.