Drupal 11 Forms Simplified Using HTMX Instead of AJAX

An article on Hash Bang Code by Phil Norton demonstrates how HTMX can be used to build dynamic forms in Drupal 11 with reduced reliance on traditional AJAX patterns.

The guide reconstructs a cascading select form—linking year, month, and day fields—using HTMX attributes instead of Drupal’s standard AJAX callbacks. Rather than managing wrappers and JavaScript logic, HTMX sends requests automatically and replaces targeted parts of the form based on server responses.

The approach works alongside Drupal’s Form API and states system. When a user updates a field, Drupal rebuilds the form using the current state, and HTMX selects and replaces only the relevant elements in the response. This enables dynamic behaviour such as adjusting available days based on month and year selections, including leap year handling.

The article also outlines implementation details such as defining routes and form classes, applying HTMX attributes to form elements, and ensuring consistent form state during rebuilds. It emphasises that responses always return the full form, requiring explicit selection of elements to avoid rendering issues.

The post provides practical examples with code and focuses on implementation rather than broader architectural analysis, but it illustrates how HTMX can reduce complexity in common form interactions within Drupal.