Phoenix LiveView Has a Free API: Build Real-Time Web Apps Without JavaScript

React needs 200KB of JavaScript for real-time features. Phoenix LiveView needs zero — it sends HTML diffs over WebSockets.

What Is Phoenix LiveView?

Phoenix LiveView lets you build rich, real-time UIs in Elixir without writing JavaScript. State lives on the server. When it changes, LiveView calculates the HTML diff and sends only the changed bytes over WebSocket.

defmodule MyAppWeb.CounterLive do
  use MyAppWeb, :live_view

  def mount(_params, _session, socket) do
    {:ok, assign(socket, count: 0)}
  end

  def handle_event("increment", _params, socket) do
    {:noreply, update(socket, :count, &(&1 + 1))}
  end

  def render(assigns) do
    ~H"""
    <h1>Count: <%= @count %></h1>
    <button phx-click="increment">+1</button>
    """
  end
end

Click the button → event sent to server over WebSocket → server updates state → server sends HTML diff → DOM patches. User sees instant update. Zero JavaScript written.

Real-Time Features in Minutes

# Live search with debounce
def handle_event("search", %{"query" => query}, socket) do
  results = MyApp.Search.find(query)
  {:noreply, assign(socket, results: results)}
end

# Template
~H"""
<input phx-change="search" phx-debounce="300" name="query" placeholder="Search...">
<ul>
  <%= for result <- @results do %>
    <li><%= result.name %></li>
  <% end %>
</ul>
"""

Live search with 300ms debounce. No useState. No useEffect. No fetch. No loading state.

Why LiveView

• Zero JavaScript — all logic in Elixir on the server
• Real-time by default — WebSocket connection, instant updates
• Scalable — Elixir/BEAM handles millions of concurrent connections
• SEO friendly — first render is server HTML, then WebSocket takes over
• Forms — live validation, uploads, multi-step wizards — all server-side
• PubSub — broadcast changes to all connected users in one line

A startup built their entire SaaS dashboard in LiveView. 50K concurrent users on a single server. Zero JavaScript frameworks.

mix phx.new my_app --live && cd my_app && mix phx.server

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Building real-time web apps? Check out my developer tools or email [e-mail].