zipaddr-jp is a free WordPress plugin designed to enhance the address input process by integrating with zipaddr services. This plugin facilitates the retrieval of address data based on Japanese zip codes, ensuring a seamless experience for users entering their information on WordPress sites. It generates a JavaScript statement to connect with the zipaddr service, allowing for efficient data handling.

The main functionality revolves around a straightforward process: after initial setup, the plugin waits for the user to input a zip code. It then sends a request to zipaddr, which searches its database and returns relevant address details in JSONP format. As users interact with the form, guidance data is displayed, ultimately filling in the address fields on the WordPress site with the retrieved prefecture, city, and region information.