Elixir

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

Installation

This library was built by the community but it's being maintained by the PostHog core team since v1.0.0. Thank you to Nick Kezhaya for building it originally.

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

Elixir

def deps do
  [
    {:posthog, "~> 1.1.0"}
  ]
end

Configuration

config/config.exs

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

# Optional configurations
config :posthog,
  json_library: Jason,   # Default JSON parser (optional)
  enabled_capture: true, # Enable/disable PostHog tracking (optional, defaults to true)
  http_client: Posthog.HTTPClient.Hackney,  # Default HTTP client (optional)
  http_client_opts: [    # HTTP client options (optional)
    timeout: 5_000,      # Request timeout in milliseconds (default: 5_000)
    retries: 3,          # Number of retries on failure (default: 3)
    retry_delay: 1_000   # Delay between retries in milliseconds (default: 1_000)
  ]

Advanced configuration

The default JSON parser is Jason but you can pass in a custom JSON library via the json_library config.

The default HTTP client is Hackney but you can pass in a custom HTTP client via the http_client config. This client should implement the Posthog.HTTPClient behaviour. For testing purposes, you'll likely want a mock HTTP client implementation.

You can refer to the library's README.md for more information on the advanced configuration options.

Development/Test mode

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

config/test.exs

config :posthog,
  enabled_capture: false # Disable tracking in test mode

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

Advanced configuration

Development/Test 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.

Community questions

Was this page useful?

Flutter

Rafael Audibert

Ian Vanagas

Ioannis Josephides