htmx and the Case for Hypermedia: Not Every App Needs a SPA

htmx had a moment this year, and the backlash-to-the-backlash discourse buried the practical question: when is server-rendered hypermedia the right architecture? Having shipped an internal tool with it, here's my grounded take.

The model in one example

htmx extends HTML with attributes that swap fragments from the server:

<input type="search" name="q"
       hx-get="/contacts/search"
       hx-trigger="input changed delay:300ms"
       hx-target="#results" />

<tbody id="results">
  <!-- server returns <tr> rows, htmx swaps them in -->
</tbody>

The server endpoint returns HTML partials, not JSON:

@app.get("/contacts/search")
def search(q: str):
    contacts = Contact.search(q)
    return render_template("partials/contact_rows.html",
                           contacts=contacts)

Search-as-you-type with debouncing, no JSON API, no client state, no build step — 14KB of library total. The mental shift: state lives on the server, and the browser displays it. Which is to say: how the web worked, plus surgical updates.

Where it genuinely wins

Internal tools, admin panels, CRUD-heavy dashboards, content sites with islands of interactivity — anywhere the interaction pattern is "user acts, server responds, view updates." For our ops tool: no bundler config, no state-synchronization bugs (there's one state, on the server), new developers productive in an hour, and the thing is fast because it ships no framework.

Where it doesn't

Optimistic UI, offline capability, complex client-side interactions (drag-and-drop builders, collaborative editing, anything canvas-based), or interfaces where round-tripping per interaction is unacceptable. And if your team's server side is a thin proxy over microservices returning JSON, generating HTML partials means building a rendering layer you don't have.

The real lesson

The htmx conversation is valuable less for the library than for the recalibration: the SPA became a default, and defaults deserve auditing. My heuristic now — count the interactions that genuinely need client-side state. If it's a handful, hypermedia plus a sprinkle of vanilla JS is less code, fewer bugs, and no hydration bill. If it's the whole product, keep React and use it well.