Phoenix LiveView
v0.20.0

View Source Installation

New projects

Phoenix v1.5+ comes with built-in support for LiveView apps. Just create your application with mix phx.new my_app --live. The --live flag has become the default on Phoenix v1.6.

Once you've created a LiveView project, refer to LiveView documentation for further information on how to use it.

Existing projects

If you are using a Phoenix version earlier than v1.5 or your app already exists, continue with the following steps.

The instructions below will serve if you are installing the latest stable version from Hex. To start using LiveView, add one of the following dependencies to your mix.exs and run mix deps.get.

If installing from Hex, use the latest version from there:

def deps do
  [
    {:phoenix_live_view, "~> 0.18"},
    {:floki, ">= 0.30.0", only: :test}
  ]
end

If you want the latest features, install from GitHub:

def deps do
  [
    {:phoenix_live_view, github: "phoenixframework/phoenix_live_view"},
    {:floki, ">= 0.30.0", only: :test}
  ]

Once installed, update your endpoint's configuration to include a signing salt. You can generate a signing salt by running mix phx.gen.secret 32:

# config/config.exs

config :my_app, MyAppWeb.Endpoint,
   live_view: [signing_salt: "SECRET_SALT"]

Next, add the following imports to your web file in lib/my_app_web.ex:

# lib/my_app_web.ex

def view do
  quote do
    # ...
    import Phoenix.Component
  end
end

def router do
  quote do
    # ...
    import Phoenix.LiveView.Router
  end
end

In that same file, update your live_view layout configuration:

# lib/my_app_web.ex

def live_view do
  use Phoenix.LiveView,
-    layout: {MyAppWeb.LayoutView, "live.html"}
+    layout: {MyAppWeb.LayoutView, :live}

  unquote(view_helpers())
end

Then add the Phoenix.LiveView.Router.fetch_live_flash/2 plug to your browser pipeline, in place of :fetch_flash:

# lib/my_app_web/router.ex

pipeline :browser do
  # ...
  plug :fetch_session
- plug :fetch_flash
+ plug :fetch_live_flash
end

Next, expose a new socket for LiveView updates in your app's endpoint module.

# lib/my_app_web/endpoint.ex

defmodule MyAppWeb.Endpoint do
  use Phoenix.Endpoint

  # ...

  socket "/live", Phoenix.LiveView.Socket,
    websocket: [connect_info: [session: @session_options]]

  # ...
end

Where @session_options are the options given to plug Plug.Session by using a module attribute. If you don't have a @session_options in your endpoint yet, here is how to create one:

  1. Find plug Plug.Session in your endpoint.ex
  plug Plug.Session
    store: :cookie,
    key: "_my_app_key",
    signing_salt: "somesigningsalt"
  1. Move the options to a module attribute at the top of your file:
  @session_options [
    store: :cookie,
    key: "_my_app_key",
    signing_salt: "somesigningsalt"
  ]
  1. Change the plug Plug.Session to use that attribute:
  plug Plug.Session, @session_options

Finally, ensure you have placed a CSRF meta tag inside the <head> tag in your layout (lib/my_app_web/templates/layout/app.html.*) before app.js is included, like so:

<meta name="csrf-token" content={Plug.CSRFProtection.get_csrf_token()} />
<script defer type="text/javascript" src={Routes.static_path(@conn, "/js/app.js")}></script>

and enable connecting to a LiveView socket in your app.js file.

// assets/js/app.js
import {Socket} from "phoenix"
import {LiveSocket} from "phoenix_live_view"

let csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute("content")
let liveSocket = new LiveSocket("/live", Socket, {params: {_csrf_token: csrfToken}})

// Connect if there are any LiveViews on the page
liveSocket.connect()

// Expose liveSocket on window for web console debug logs and latency simulation:
// >> liveSocket.enableDebug()
// >> liveSocket.enableLatencySim(1000)
// The latency simulator is enabled for the duration of the browser session.
// Call disableLatencySim() to disable:
// >> liveSocket.disableLatencySim()
window.liveSocket = liveSocket

The JavaScript above expects phoenix_live_view to be available as a JavaScript dependency. Let's do that.

npm dependencies

If using npm, you need to add LiveView to your assets/package.json. For a regular project, do:

{
  "dependencies": {
    "phoenix": "file:../deps/phoenix",
    "phoenix_html": "file:../deps/phoenix_html",
    "phoenix_live_view": "file:../deps/phoenix_live_view"
  }
}

However, if you're adding phoenix_live_view to an umbrella project, the dependency paths should be modified appropriately:

{
  "dependencies": {
    "phoenix": "file:../../../deps/phoenix",
    "phoenix_html": "file:../../../deps/phoenix_html",
    "phoenix_live_view": "file:../../../deps/phoenix_live_view"
  }
}

Now run the next commands from the root of your web app project:

npm install --prefix assets

If you had previously installed phoenix_live_view and want to get the latest javascript, then force an install with:

npm install --force phoenix_live_view --prefix assets

Layouts

LiveView does not use the default app layout. Instead, you typically call put_root_layout in your router to specify a layout that is used by both "regular" views and live views. In your router, do:

# lib/my_app_web/router.ex

pipeline :browser do
  # ...
  plug :put_root_layout, html: {MyAppWeb.LayoutView, :root}
  # ...
end

The layout given to put_root_layout is typically very barebones, with mostly <head> and <body> tags. For example:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta name="csrf-token" content={Plug.CSRFProtection.get_csrf_token()} />
    <Phoenix.Component.live_title><%= assigns[:page_title] || "MyApp" %></Phoenix.Component.live_title>
    <link rel="stylesheet" href={Routes.static_path(@conn, "/css/app.css")} />
    <script defer type="text/javascript" src={Routes.static_path(@conn, "/js/app.js")}></script>
  </head>
  <body>
    <%= @inner_content %>
  </body>
</html>

Once you have specified a root layout, app.html.heex will be rendered within your root layout for all non-LiveViews. You may also optionally define a live.html.heex layout to be used across all LiveViews, as we will describe in the next section.

Optionally, you can add a phx-track-static to all script and link elements in your layout that use src and href. This way you can detect when new assets have been deployed by calling static_changed?.

<link phx-track-static rel="stylesheet" href={Routes.static_path(@conn, "/css/app.css")} />
<script phx-track-static defer type="text/javascript" src={Routes.static_path(@conn, "/js/app.js")}></script>

Progress animation

If you want to show a progress bar as users perform live actions, we recommend using topbar.

You can either add a copy of topbar to assets/vendor/topbar.js or add it as a npm dependency by calling:

$ npm install --prefix assets --save topbar

Then customize LiveView to use it in your assets/js/app.js, right before the liveSocket.connect() call:

// Show progress bar on live navigation and form submits
import topbar from "topbar"
topbar.config({barColors: {0: "#29d"}, shadowColor: "rgba(0, 0, 0, .3)"})
window.addEventListener("phx:page-loading-start", info => topbar.show())
window.addEventListener("phx:page-loading-stop", info => topbar.hide())

Alternatively, you can also delay showing the topbar and wait if the results do not appear within 200ms:

// Show progress bar on live navigation and form submits
import topbar from "topbar"
topbar.config({barColors: {0: "#29d"}, shadowColor: "rgba(0, 0, 0, .3)"})

window.addEventListener("phx:page-loading-start", () => {
  topbar.show(200)
})

window.addEventListener("phx:page-loading-stop", () => {
  topbar.hide()
})

Location for LiveView modules

By convention your LiveView modules and heex templates should be placed in lib/my_app_web/live/ directory.