HTMX in Drupal Core: The Ajax API Replacement That Is Long Overdue

For over a decade, Drupal developers have relied on Drupal.ajax — a powerful but heavy abstraction layer over jQuery — to handle dynamic interactions. With jQuery's slow sunset and the rise of "HTML-over-the-wire" paradigms, the HTMX in Drupal Core initiative is the most sensible thing to happen to Drupal's frontend in years.

I built a proof-of-concept module to test what this migration actually looks like in practice.

The Problem with Drupal.ajax

"The server returns a JSON array of commands (insert, remove, invoke), which the client must parse and execute."

— Drupal Ajax Framework, Core Documentation

Context

Drupal's Ajax system was built when jQuery was the only game in town and server-rendered HTML was unfashionable. The framework sends a proprietary JSON command protocol from PHP to JavaScript, which the client interprets and executes. Every other modern framework has moved past this pattern.

Problem	Impact
Proprietary JSON command protocol	Developers must learn Drupal-specific API instead of web standards
Tight jQuery coupling	Blocks migration to modern JS
Client-side command runner	Complexity that HTMX eliminates entirely
Heavy payload	JSON commands instead of plain HTML fragments

The HTMX Solution

HTMX offers a simpler, declarative model. You define interactions in HTML attributes, and the server returns HTML fragments. No custom JSON protocol. No complex client-side command runner.

Code Comparison

Here is how a simple "Get Server Time" feature looks in both paradigms.

The Controller

HTMX (New)

src/Controller/HtmxDemoController.php

public function time() {
$time = $this->time->getCurrentTime();
$formatted = $this->dateFormatter->format($time, 'long');

// Just return HTML. Simpler, lighter.
return new Response("<div>Time: $formatted</div>");
}

Drupal Ajax (Old)

src/Controller/AjaxDemoController.php

public function timeAjax() {
$time = $this->time->getCurrentTime();
$formatted = $this->dateFormatter->format($time, 'long');

// Construct a JSON response with commands.
$response = new AjaxResponse();
$response->addCommand(new HtmlCommand('#time-container', "<div>Time: $formatted</div>"));
return $response;
}

The Frontend

HTMX (New)

templates/htmx-demo.html.twig

<!-- Declarative: Get from URL, swap into target -->
<button hx-get="/htmx-demo/time"
hx-target="#container"
hx-swap="innerHTML">
Get Time
</button>

Drupal Ajax (Old)

templates/ajax-demo.html.twig

<!-- Requires 'use-ajax' class and implicit conventions -->
<a href="/htmx-demo/time-ajax" class="use-ajax">
Get Time
</a>

Side-by-Side Comparison

Aspect	Drupal Ajax	HTMX
Server response	Proprietary JSON commands	Standard HTML fragments
Client library	jQuery + drupal.ajax	htmx.js (~14KB)
Learning curve	Drupal-specific API	HTML attributes (web standard)
JS knowledge needed	Must understand AjaxCommand API	Minimal to none
Backend approach	Build AjaxResponse with commands	Return HTML string or render array
Debugging	Inspect JSON command array	Inspect HTML response in Network tab
Framework coupling	Drupal-only	Framework-agnostic

Reality Check

Full core replacement is a massive undertaking. Drupal's Ajax system is deeply embedded in Form API, Views, field widgets, and dozens of contrib modules. The benefits of HTMX are clear, but the migration path will take years and involve painful backward-compatibility work. Do not expect to rip out drupal.ajax from your contrib modules next quarter.

Why This Matters

Who benefits and how

• Frontend devs don't need to learn the AjaxCommand PHP API.
• Backend devs can return standard render arrays or templates.
• Performance improves by removing the jQuery and drupal.ajax overhead.
• New contributors face a lower barrier to entry — HTMX is HTML, not a Drupal-specific protocol.
• The Drupal ecosystem aligns with the broader web ecosystem, making it more accessible to developers coming from other frameworks.

The Code

View Code

Why this matters for Drupal and WordPress

For Drupal module developers, HTMX adoption in core means rewriting Ajax-heavy contrib modules to return HTML fragments instead of JSON command arrays — starting with custom form widgets, Views exposed filters, and admin UI interactions. WordPress developers already familiar with HTMX through plugins like flavor or admin-ajax alternatives will find that Drupal's move validates the HTML-over-the-wire pattern at CMS-core level, making cross-CMS frontend skills more transferable. Agencies maintaining both Drupal and WordPress sites benefit from a converging frontend model where server-rendered HTML replaces framework-specific JavaScript abstractions.

What I Learned

• HTMX is a natural fit for Drupal's server-rendered philosophy. The paradigm match is almost too perfect.
• The migration from Ajax to HTMX is straightforward for new features. Retrofitting existing Ajax-heavy modules is where the real work lives.
• Removing the JSON command protocol eliminates an entire category of Drupal-specific knowledge that new developers currently have to learn.
• This initiative deserves more attention and contributor effort than it is currently getting.

References

• HTMX Now in Drupal Core — Ajax API replacement initiative

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