Elixir

This library provides an Elixir HTTP client for PostHog. See the repository for more information.

Installation

This library was built by the community and is not maintained by the PostHog core team.

The package can be installed by adding posthog to your list of dependencies in mix.exs:

Elixir

def deps do
  [
    {:posthog, "~> 1.0.0"}
  ]
end

Configuration

Elixir

config :posthog,
  api_url: "https://us.i.posthog.com",
  api_key: "<ph_project_api_key>"

Optionally, you can pass in a :json_library key. The default JSON parser is Jason.

You'll also need to include the posthog application in your supervision tree. You can do this in two ways:

Add it to your application function:

Elixir

# mix.exs
def application do
  [
    extra_applications: [
      # ... your existing extra applications
      :posthog
    ]
  ]
end

Add it to your existing MyApp.Application module:

Elixir

# lib/my_app/application.ex
defmodule MyApp.Application do
  use Application

  def start(_type, _args) do
    children = [
      # ... your existing children
      {Posthog.Application, []}
    ]

    opts = [strategy: :one_for_one, name: MyApp.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

Development mode

If you are running in development or test mode, you can pass in a capture_disabled: false value to the config. This causes events to be dropped instead of sent to PostHog.

Elixir

config :posthog,
  capture_disabled: false

Capturing events

You can send custom events using capture:

Elixir

Posthog.capture("user_signed_up", distinct_id_of_the_user)

Tip: We recommend using a [object] [verb] format for your event names, where [object] is the entity that the behavior relates to, and [verb] is the behavior itself. For example, project created, user signed up, or invite sent.

Setting event properties

Optionally, you can include additional information with the event by including a properties object:

Elixir

Posthog.capture("user_signed_up", distinct_id_of_the_user, %{
  login_type: "email",
  is_free_trial: true
})

Batching events

To capture multiple events at once, use batch():

Elixir

Posthog.batch([{"user_signed_up", distinct_id_of_the_user, %{}}])

Feature flags

PostHog's feature flags enable you to safely deploy and roll back new features as well as target specific users and groups with them.

Elixir supports a subset of what our feature flag API provides.

Boolean feature flags

Elixir

is_my_flag_enabled = Posthog.feature_flag_enabled?("flag-key", "distinct_id_of_your_user")

if is_my_flag_enabled
    # Do something differently for this user
    # Optional: fetch the payload
    {:ok, feature_flag} = Posthog.feature_flag("flag-key", "distinct_id_of_your_user")
end

Multivariate feature flags

Elixir

{:ok, feature_flag} = Posthog.feature_flag("flag-key", "distinct_id_of_your_user")
#  %Posthog.FeatureFlag{ name: "flag-key", payload: %{"variant-1" => "value-1", "variant-2" => "value-2"}, enabled: "variant-2" }

if feature_flag.enabled == 'variant-2' # replace 'variant-2' with the key of your variant
    # Do something differently for this user
end

Fetching all feature flags

Elixir

Posthog.feature_flags("distinct_id_of_your_user")

{:ok,
 %{
   "featureFlagPayloads" => %{
     "feature-1" => 1,
     "feature-2" => %{"variant-1" => "value-1", "variant-2" => "value-2"}
   },
   "featureFlags" => %{"feature-1" => true, "feature-2" => "variant-2"}
 }}

More documentation can be found in the repository.

Thanks

Thanks to nkezhaya for initially contributing this library. The library is maintained by the PostHog team since February 2025.

Which features are available in this library?

Installation

Configuration

Development mode

Capturing events

Setting event properties

Batching events

Feature flags

Boolean feature flags

Multivariate feature flags

Fetching all feature flags

Thanks

Questions? Ask Max AI.

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