Flutter

This is an optional library you can install if you're working with Flutter. It uses an internal queue to make calls fast and non-blocking. It also batches requests and flushes asynchronously, making it perfect to use in any part of your mobile app.

PostHog supports the iOS, macOS, Android and Web platforms.

Installation

PostHog is available for install via Pub.

Configuration

Set your PostHog API key and change the automatic event tracking on if you wish the library to take care of it for you.

Remember that the application lifecycle events won't have any special context set for you by the time it is initialized. If you are using a self-hosted instance of PostHog you will need to have the public hostname or IP for your instance as well.

To start, add posthog_flutter to your pubspec.yaml:

pubspec.yaml

# rest of your code

dependencies:
  flutter:
    sdk: flutter
  posthog_flutter: ^4.0.1

# rest of your code

Then complete the set up for each platform:

Android setup

For Android, add your PostHog configuration to your AndroidManifest.xml file located in the android/app/src/main:

android/app/src/main/AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="your.package.name">
    <application>
        <!-- ... other configuration ... -->
        <meta-data android:name="com.posthog.posthog.API_KEY" android:value="<ph_project_api_key>" />
        <meta-data android:name="com.posthog.posthog.POSTHOG_HOST" android:value="<ph_client_api_host>" />  <!-- usually 'https://us.i.posthog.com' or 'https://eu.i.posthog.com' -->
        <meta-data android:name="com.posthog.posthog.TRACK_APPLICATION_LIFECYCLE_EVENTS" android:value="true" />
        <meta-data android:name="com.posthog.posthog.DEBUG" android:value="true" />
    </application>
</manifest>

You'll also need to update the minimum Android SDK version to 21 in android/app/build.gradle:

android/app/build.gradle

// rest of your config

    defaultConfig {
      minSdkVersion 21
      // rest of your config
    }

// rest of your config

iOS setup

For iOS, you'll need to have Cocoapods installed. Then add your PostHog configuration to the Info.plist file located in the ios/Runner directory:

ios/Runner/Info.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<!-- rest of your configuration -->
  <key>com.posthog.posthog.API_KEY</key>
  <string><ph_project_api_key></string>
  <key>com.posthog.posthog.POSTHOG_HOST</key>
  <string><ph_client_api_host></string>
  <key>com.posthog.posthog.CAPTURE_APPLICATION_LIFECYCLE_EVENTS</key>
  <true/>
  <key>com.posthog.posthog.DEBUG</key>
  <true/>
</dict>
</plist>

Then you need to set the minimum platform version to iOS 13.0 in your Podfile:

ios/Podfile

platform :ios, '13.0'

# rest of your config

Web setup

For Web, add your Web snippet (which you can find in your project settings) in the <header> of your web/index.html file:

web/index.html

<!DOCTYPE html>
<html>

<head>
  <!-- ... other head elements ... -->

  <script async>
    !function(t,e){var o,n,p,r;e.__SV||(window.posthog=e,e._i=[],e.init=function(i,s,a){function g(t,e){var o=e.split(".");2==o.length&&(t=t[o[0]],e=o[1]),t[e]=function(){t.push([e].concat(Array.prototype.slice.call(arguments,0)))}}(p=t.createElement("script")).type="text/javascript",p.async=!0,p.src=s.api_host+"/static/array.js",(r=t.getElementsByTagName("script")[0]).parentNode.insertBefore(p,r);var u=e;for(void 0!==a?u=e[a]=[]:a="posthog",u.people=u.people||[],u.toString=function(t){var e="posthog";return"posthog"!==a&&(e+="."+a),t||(e+=" (stub)"),e},u.people.toString=function(){return u.toString(1)+".people (stub)"},o="capture identify alias people.set people.set_once set_config register register_once unregister opt_out_capturing has_opted_out_capturing opt_in_capturing reset isFeatureEnabled onFeatureFlags getFeatureFlag getFeatureFlagPayload reloadFeatureFlags group updateEarlyAccessFeatureEnrollment getEarlyAccessFeatures getActiveMatchingSurveys getSurveys onSessionId".split(" "),n=0;n<o.length;n++)g(u,o[n]);e._i.push([i,s,a])},e.__SV=1)}(document,window.posthog||[]);
    posthog.init(
      '<ph_project_api_key>',
      {
        api_host:https://us.i.posthog.com, // 'https://us.i.posthog.com' or 'https://eu.i.posthog.com'
      }
    )
  </script>
</head>

<!-- other elements -->

</html>

For more information please check: https://posthog.com/docs/libraries/js

Usage

Example

Dart

import 'package:flutter/material.dart';
import 'package:posthog_flutter/posthog_flutter.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      navigatorObservers: [
        // The PosthogObserver records screen views automatically
        PosthogObserver(),
      ],
      home: Scaffold(
        appBar: AppBar(
          title: Text('PostHog example app'),
        ),
        body: Center(
          child: FlatButton(
            child: Text('TRACK ACTION WITH PostHog'),
            onPressed: () async {
              await Posthog().capture(
                eventName: 'ButtonClicked',
                properties: {
                  'foo': 'bar',
                  'number': 1337,
                  'clicked': true,
                },
              );
            },
          ),
        ),
      )
    );
  }
}

Capturing events

You can send custom events using capture:

Dart

await Posthog().capture(
  eventName: 'user_signed_up',
);

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 also include additional information in the event by setting the properties value:

Dart

await Posthog().capture(
  eventName: 'user_signed_up',
  properties: {
    'login_type': 'email',
    'is_free_trial': true
  }
);

Autocapture

PostHog autocapture automatically tracks the following events for you:

Application Opened - when the app is opened from a closed state or when the app comes to the foreground (e.g. from the app switcher)
Application Backgrounded - when the app is sent to the background by the user
Application Installed - when the app is installed.
Application Updated - when the app is updated.
$screen - when the user navigates (if using navigatorObservers or go_router)

Identifying users

We highly recommend reading our section on Identifying users to better understand how to correctly use this method.

Using identify, you can associate events with specific users. This enables you to gain full insights as to how they're using your product across different sessions, devices, and platforms.

An identify call has the following arguments:

userId: Required. A unique identifier for your user. Typically either their email or database ID.
userProperties: Optional. A dictionary with key:value pairs to set the user properties
userPropertiesSetOnce: Optional. Similar to userProperties. See the difference between userProperties and userPropertiesSetOnce

Dart

await Posthog().identify(
  userId: emailController.text, 
  userProperties: {"name": "Peter Griffin", "email": "peter@familyguy.com"},
  userPropertiesSetOnce: {"date_of_first_log_in": "2024-03-01"}
);

You should call identify as soon as you're able to. Typically, this is every time your app loads for the first time as well as directly after your user logs in. This ensures that events sent during your user's sessions are correctly associated with them.

When you call identify, all previously tracked anonymous events will be linked to the user.

Alias

Sometimes, you may want to assign multiple distinct IDs to a single user. This is helpful in scenarios where your primary distinct ID may be inaccessible. For example, if a distinct ID which is typically used on the frontend is not available in certain parts of your backend code. In this case, you can use alias to assign another distinct ID to the same user.

We strongly recommend reading our docs on alias to best understand how to correctly use this method.

Super Properties

Super Properties are properties associated with events that are set once and then sent with every capture call, be it a $screen, or anything else.

They are set using Posthog().register, which takes a key and value, and they persist across sessions.

For example, take a look at the following call:

Dart

import 'package:posthog_flutter/posthog_flutter.dart';

await Posthog().register("team_id", 22)

The call above ensures that every event sent by the user will include "team_id": 22. This way, if you filtered events by property using team_id = 22, it would display all events captured on that user after the Posthog().register call, since they all include the specified Super Property.

However, please note that this does not store properties against the User, only against their events. To store properties against the User object, you should use Posthog().identify. More information on this can be found on the Sending User Information section.

Removing stored Super Properties

Super Properties are persisted across sessions so you have to explicitly remove them if they are no longer relevant. In order to stop sending a Super Property with events, you can use Posthog().unregister, like so:

Dart

import 'package:posthog_flutter/posthog_flutter.dart';

await Posthog().unregister("team_id")

This will remove the Super Property and subsequent events will not include it.

If you are doing this as part of a user logging out you can instead simply use Posthog().reset which takes care of clearing all stored Super Properties and more.

Group analytics

Group analytics allows you to associate the events for that person's session with a group (e.g. teams, organizations, etc.). Read the Group Analytics guide for more information.

Note: This is a paid feature and is not available on the open-source or free cloud plan. Learn more here.

Associate the events for this session with a group

Dart

await Posthog().group(groupType: "company", groupKey: "company_id_in_your_db");

Associate the events for this session with a group AND update the properties of that group

Swift

await Posthog().group(
  groupType: "company", 
  groupKey: "company_id_in_your_db", 
  groupProperties: {
    "name": "ACME Corp"
});

The name is a special property which is used in the PostHog UI for the name of the Group. If you don't specify a name property, the group ID will be used instead.

Feature Flags

PostHog's feature flags enable you to safely deploy and roll back new features.

Boolean feature flags

Dart

if (await Posthog().isFeatureEnabled('flag-key')) {
    // Do something differently for this user

    // Optional: fetch the payload
    final matchedFlagPayload = await Posthog().getFeatureFlagPayload('flag-key');
}

Multivariate feature flags

Dart

if (await Posthog().getFeatureFlag('flag-key') == 'variant-key') { // replace 'variant-key' with the key of your variant
    // Do something differently for this user

    // Optional: fetch the payload
    final matchedFlagPayload = await Posthog().getFeatureFlagPayload('flag-key');
}

Ensuring flags are loaded before usage

Every time a user loads a screen, we send a request in the background to fetch the feature flags that apply to that user. We store those flags in the storage.

This means that for most screens, the feature flags are available immediately – except for the first time a user visits.

Reloading feature flags

Feature flag values are cached. If something has changed with your user and you'd like to refetch their flag values, call:

Dart

await Posthog().reloadFeatureFlags();

Session replay

Note: Session replay is only supported on the Flutter Web environment.

To set up session replay in your project, all you need to do is install the Flutter SDK and enable "Record user sessions" in your project settings.

Issues

Please file any issues, bugs, or feature requests in our GitHub repository.

Contributing

If you wish to contribute a change to this repo, please send a Pull Request.

Which features are available in this library?

Installation

Configuration

Android setup

iOS setup

Web setup

Usage

Example

Capturing events

Setting event properties

Autocapture

Identifying users

Alias

Super Properties

Removing stored Super Properties

Group analytics

Feature Flags

Boolean feature flags

Multivariate feature flags

Ensuring flags are loaded before usage

Reloading feature flags

Session replay

Issues

Contributing

Questions?

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