AbsintheAltair

A Plug for embedding the Altair GraphQL Client into Phoenix and Absinthe applications.

Altair is a feature-rich GraphQL IDE with support for subscriptions, file uploads, query collections, environments, and more. This library serves the Altair single-page application directly from your Elixir app, loading assets from CDN.

Installation

Add absinthe_altair to your list of dependencies in mix.exs:

def deps do
  [
    {:absinthe_altair, "~> 2026.4.2"}
  ]
end

Usage

Add a forward to your Phoenix router:

# lib/my_app_web/router.ex
scope "/" do
  forward "/altair", AbsintheAltair, endpoint_url: "/api/graphql"

  forward "/api/graphql", Absinthe.Plug, schema: MyAppWeb.Schema
end

Then visit http://localhost:4000/altair in your browser.

With Subscriptions

forward "/altair", AbsintheAltair,
  endpoint_url: "/api/graphql",
  subscriptions_endpoint: "ws://localhost:4000/socket/websocket",
  subscriptions_protocol: "graphql-ws"

With Dynamic Headers

Configuration values can be {module, function} tuples resolved at request time. The function may accept a Plug.Conn argument (arity 1) or no arguments (arity 0):

forward "/altair", AbsintheAltair,
  endpoint_url: "/api/graphql",
  initial_headers: {MyAppWeb.AltairHelpers, :default_headers}

# In lib/my_app_web/altair_helpers.ex
defmodule MyAppWeb.AltairHelpers do
  def default_headers(conn) do
    %{"Authorization" => "Bearer " <> (conn.assigns[:token] || "")}
  end
end

Dual-Mode (UI + API on Same Path)

When :schema is set and absinthe_plug is available as a dependency, non-HTML requests (e.g. Accept: application/json) are delegated to Absinthe.Plug:

forward "/graphql", AbsintheAltair,
  schema: MyAppWeb.Schema,
  endpoint_url: "/graphql"

Requests with Accept: text/html get the Altair UI; all other requests are handled as GraphQL API calls.

Configuration Reference

Any Altair configuration property can be passed as a snake_case atom option. Keys are automatically converted to camelCase for JavaScript (e.g. :initial_query becomes initialQuery). The table below lists common options — it is not exhaustive.

Option	Type	Default	Description
`:endpoint_url`	`binary \| {mod, fun}`	`nil`	GraphQL endpoint URL. When `nil`, defaults to `window.location` in the browser.
`:subscriptions_endpoint`	`binary \| {mod, fun}`	`nil`	WebSocket URL for subscriptions.
`:subscriptions_protocol`	`binary`	`nil`	Protocol: `"ws"`, `"graphql-ws"`, `"graphql-sse"`, `"app-sync"`, or `"action-cable"`.
`:initial_query`	`binary`	`""`	Pre-populated GraphQL query.
`:initial_variables`	`binary`	`""`	Pre-populated variables.
`:initial_headers`	`map \| {mod, fun}`	`%{}`	Default request headers.
`:initial_settings`	`map`	`nil`	Altair application settings.
`:altair_version`	`binary`	`"8.5.2"`	`altair-static` npm package version to load from CDN.
`:schema`	`atom`	`nil`	Absinthe schema module. Enables API delegation for non-HTML requests when `absinthe_plug` is available.

For the full list of supported Altair options, see the AltairConfig API reference.

How It Works

The plug serves an HTML page with a <base href> pointing to the altair-static distribution on jsDelivr CDN. All of Altair's JavaScript, CSS, fonts, and image assets are loaded from the CDN relative to this base URL. Configuration is passed to the Altair SPA in its init function.

No local static files are needed. The tradeoff is that an internet connection is required for the browser to load Altair's assets.

License

Copyright (c) 2026 Jeffrey Sandberg

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.