Instrument Logs

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Flutter Logs installation

Canonical URL: https://posthog.com/docs/logs/installation/flutter

Cloud region: This page uses US Cloud hosts. For an EU Cloud project, use https://eu.posthog.com instead of https://us.posthog.com or https://app.posthog.com (app host for links).

On this page

• Install posthog_flutter

• Configure logs in your PostHogConfig

• Capture logs

• Test your setup

• Tune buffering, rate cap, and resource attributes

• Filter or redact with beforeSend

• Next steps

The PostHog Flutter SDK has built-in support for capturing structured Logs from your Flutter app across mobile and web. The SDK handles the OTLP encoding, batching, and flushing — and on mobile, on-disk persistence across app restarts and app-lifecycle integration (web buffers in memory via posthog-js). You just call Posthog().captureLog(...) or Posthog().logger.{trace,debug,info,warn,error,fatal}(...).

Manual capture only. Logs are emitted by your code. The SDK does not autocapture system log streams (print, debugPrint, or dart:developer's log).

Minimum version: posthog_flutter 5.27.0 or later (the release that adds Logs support). On mobile it pulls in posthog-android 3.48.0 or later automatically.

1. 1

   Install posthog_flutter

   Required

   If you haven't installed posthog_flutter yet, follow the steps below. For full details, see the Flutter SDK guide.

   CocoaPods is becoming read-only. CocoaPods has announced the following schedule for its public specs repository:

   • November 2–6, 2026: A read-only dry run will prevent us from publishing new PostHog iOS SDK versions to CocoaPods.

   • December 2, 2026 onward: The repository will be permanently read-only. New PostHog iOS SDK versions will only be available through Swift Package Manager (SPM).

   Existing native SDK versions will remain available through CocoaPods. To keep receiving native SDK updates on iOS and macOS, migrate your Flutter app to SPM. The posthog_flutter package supports SPM, and Flutter 3.44 and later enable it by default. On earlier Flutter versions that support SPM, or if you disabled it, run flutter config --enable-swift-package-manager, then rebuild your app. Follow Flutter's SPM migration guide for project setup and troubleshooting.

   This change does not affect posthog_flutter releases on pub.dev, Android, or web.

   PostHog is available for install via Pub.

   Configuration

   Set your PostHog project token and enable automatic event tracking if you want the library to capture lifecycle events 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

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   # rest of your code
   
   dependencies:
     flutter:
       sdk: flutter
     posthog_flutter: ^5.26.0
   
   # rest of your code

   Then complete the setup for each platform:

   For Session Replay and Surveys, you must set up the SDK manually by disabling the com.posthog.posthog.AUTO_INIT mode.

   Android setup

   There are 2 ways of initializing the SDK, automatically and manually.

   Automatically:

   Add your PostHog configuration to your AndroidManifest.xml file located in the android/app/src/main:

   android/app/src/main/AndroidManifest.xml

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   <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="your.package.name">
       <application>
           <!-- ... other configuration ... -->
           <meta-data android:name="com.posthog.posthog.PROJECT_TOKEN" android:value="<ph_project_token>" />
           <meta-data android:name="com.posthog.posthog.POSTHOG_HOST" android:value="https://us.i.posthog.com" />  <!-- usually 'https://us.i.posthog.com' or 'https://eu.i.posthog.com' -->
           <!-- com.posthog.posthog.CAPTURE_APPLICATION_LIFECYCLE_EVENTS is enabled by default since version 5.23.0 (previously named TRACK_APPLICATION_LIFECYCLE_EVENTS, which still works as an alias) -->
           <meta-data android:name="com.posthog.posthog.DEBUG" android:value="true" />
       </application>
   </manifest>

   Or manually (more control and more configurations available):

   Add your PostHog configuration to your AndroidManifest.xml file located in the android/app/src/main:

   android/app/src/main/AndroidManifest.xml

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   <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="your.package.name">
       <application>
           <!-- ... other configuration ... -->
           <meta-data android:name="com.posthog.posthog.AUTO_INIT" android:value="false" />
       </application>
   </manifest>

   In both cases, you'll also need to update the minimum Android SDK version to 23 in android/app/build.gradle:

   android/app/build.gradle

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   // rest of your config
   
       defaultConfig {
           minSdkVersion 23
           // rest of your config
       }
   
   // rest of your config

   iOS setup

   There are 2 ways of initializing the SDK, automatically and manually.

   The SDK supports both CocoaPods and Swift Package Manager (SPM). Flutter 3.44 and later enable SPM by default. On earlier versions, or if you disabled SPM, enable it with flutter config --enable-swift-package-manager.

   Automatically:

   Add your PostHog configuration to the Info.plist file located in the ios/Runner directory:

   ios/Runner/Info.plist

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   <?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.PROJECT_TOKEN</key>
       <string><ph_project_token></string>
       <key>com.posthog.posthog.POSTHOG_HOST</key>
       <string>https://us.i.posthog.com</string>
       <!-- com.posthog.posthog.CAPTURE_APPLICATION_LIFECYCLE_EVENTS is enabled by default since version 5.23.0 -->
       <key>com.posthog.posthog.DEBUG</key>
       <true/>
   </dict>
   </plist>

   Or manually (more control and more configurations available):

   Add your PostHog configuration to the Info.plist file located in the ios/Runner directory:

   ios/Runner/Info.plist

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   <?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.AUTO_INIT</key>
       <false/>
   </dict>
   </plist>

   In both cases, you'll need to set the minimum platform version to iOS 13.0.

   For CocoaPods projects, set it in your Podfile:

   ios/Podfile

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   platform :ios, '13.0'
   # rest of your config

   For Swift Package Manager projects without a Podfile, set the Minimum Deployments version to iOS 13.0 for the Runner target in Xcode (Runner > General > Minimum Deployments). After you change Minimum Deployments, regenerate the iOS project's configuration files:

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   flutter build ios --config-only

   Dart setup (For manual step only)

   If you followed the automatic SDK setup, then there's no more configuration needed in Dart.

   If you followed the manual SDK setup:

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   import 'package:flutter/material.dart';
   
   import 'package:posthog_flutter/posthog_flutter.dart';
   
   Future<void> main() async {
     // init WidgetsFlutterBinding if not yet
     WidgetsFlutterBinding.ensureInitialized();
     final config = PostHogConfig('<ph_project_token>');
     config.debug = true;
     // captureApplicationLifecycleEvents is enabled by default since version 5.23.0
     config.host = 'https://us.i.posthog.com';
     await Posthog().setup(config);
     runApp(MyApp());
   }

   Web setup

   If your project has a web/ directory, this step is required. Posthog().setup() is a no-op on web, so a web build without the snippet below captures nothing.

   Add your Web snippet (which you can find in your project settings) in the <header> of your web/index.html file. Write your project token into the snippet as a literal string. It's public, the same token ships to every visitor, and it needs no build-time or deploy-time injection:

   web/index.html

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   <!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.crossOrigin = "anonymous"),
                 (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 || [],
                   Object.defineProperty(u, "toString", {
                     configurable: !0,
                     enumerable: !0,
                     writable: !0,
                     value: function (t) {
                       var e = "posthog";
                       return ("posthog" !== a && (e += "." + a), t || (e += " (stub)"), e);
                     },
                   }),
                   Object.defineProperty(u.people, "toString", {
                     configurable: !0,
                     enumerable: !0,
                     writable: !0,
                     value: 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 getFeatureFlagResult reloadFeatureFlags group updateEarlyAccessFeatureEnrollment getEarlyAccessFeatures getActiveMatchingSurveys getSurveys getNextSurveyStep 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_token>", {
           api_host: "https://us.i.posthog.com", // 'https://us.i.posthog.com' or 'https://eu.i.posthog.com'
           defaults: "2026-08-30",
         });
       </script>
     </head>
   
     <!-- other elements -->
   </html>

   For more information please check: /docs/libraries/js

2. 2

   Configure logs in your PostHogConfig

   Required

   Configure Logs through config.logsConfig before calling Posthog().setup(...). All fields are optional; unset fields fall back to the native defaults, which are tuned for mobile (cellular bandwidth, battery, app lifecycle).

   Copy

   final config = PostHogConfig('<ph_project_token>');
   config.host = 'https://us.i.posthog.com';
   config.logsConfig.serviceName = 'my-app';        // OTLP service.name – shown in the Logs UI
   config.logsConfig.environment = 'production';    // OTLP deployment.environment
   config.logsConfig.serviceVersion = '1.2.3';      // OTLP service.version
   await Posthog().setup(config);

   These resource attributes are captured at setup(...) and apply to every batch.

   Web behavior. On Flutter Web, the SDK attaches to an already-initialized posthog-js instance, so config.logsConfig is not applied on web. Configure your log options in the posthog.init({...}) call in your web/index.html instead. captureLog and logger still work on web (they are forwarded to posthog-js), and beforeSend still runs (in Dart) on web. Web also requires a recent posthog-js build that exposes captureLog.

   For example, set the same service identity on the posthog-js snippet in web/index.html:

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   <script>
     posthog.init('<ph_project_token>', {
       api_host: 'https://us.i.posthog.com',
       logs: {
         serviceName: 'my-app',
         environment: 'production',
         serviceVersion: '1.2.3',
       },
     })
   </script>

   See the JavaScript Logs installation guide for the full posthog-js logs config.

3. 3

   Capture logs

   Required

   Use Posthog().logger for the per-level convenience API, or Posthog().captureLog for full control over level, attributes, and trace context.

   Copy

   import 'package:posthog_flutter/posthog_flutter.dart';
   
   // Per-level convenience methods
   Posthog().logger.info('checkout completed', {'order_id': 'ord_789', 'amount_cents': 4999});
   Posthog().logger.warn('payment retry', {'attempt': 2});
   Posthog().logger.error('payment failed', {'code': 'E001'});
   
   // Lower-level API for custom severity / trace context
   Posthog().captureLog(
     body: 'checkout failed',
     level: PostHogLogSeverity.error,
     attributes: {'order_id': 'ord_789', 'step': 'auth'},
     traceId: '4bf92f3577b34da6a3ce929d0e0e4736',  // optional W3C trace context (32 hex chars)
     spanId: '00f067aa0ba902b7',                   // optional W3C span (16 hex chars)
     traceFlags: 1,
   );

   The per-level facade methods are trace, debug, info, warn, error, and fatal, each taking a String body and an optional Map<String, Object> of attributes. Available severity levels for captureLog are PostHogLogSeverity.trace, .debug, .info, .warn, .error, and .fatal.

   The optional W3C trace fields (traceId, spanId, traceFlags) are available on captureLog only, not on the logger facade.

   Records are buffered, batched, persisted to disk, and flushed automatically – every 30 seconds, when the buffer hits the threshold, when the app moves to the background, or on Posthog().flush(). flush() drains events, Session Replay, and Logs together.

   Each record is automatically tagged with the current distinct ID, session ID, active feature flags, and (on mobile) the current screen and app foreground/background state at the moment of capture. On web, url.full is tagged instead of screen name and app state.

4. 4

   Test your setup

   Recommended

   1. Capture a test log from your app:

      Copy

      Posthog().logger.info('hello from Flutter');
      Posthog().flush();

   2. Open the PostHog Logs UI.

   3. Filter by service.name = 'my-app' (or whatever value you set above).

   You should see your record arrive within a few seconds.

   View your Logs in PostHog

5. 5

   Tune buffering, rate cap, and resource attributes

   Optional

   The logsConfig has knobs for high-volume apps:

   Copy

   final config = PostHogConfig('<ph_project_token>');
   config.logsConfig.serviceName = 'my-app';
   config.logsConfig.flushInterval = Duration(seconds: 5);      // default 30s
   config.logsConfig.maxBufferSize = 200;                       // default 1000
   config.logsConfig.maxBatchSize = 50;                         // default 50
   config.logsConfig.flushAt = 20;                              // default 20
   config.logsConfig.rateCapMaxLogs = 5000;                     // default 500
   config.logsConfig.rateCapWindow = Duration(seconds: 60);     // default 10s
   config.logsConfig.resourceAttributes = {'host.name': 'device-01'};
   await Posthog().setup(config);

   Full configuration reference:

   Field	Default	What it does
   serviceName	app bundle id (iOS) / app namespace (Android)	OTLP service.name resource attribute
   serviceVersion	app version	OTLP service.version resource attribute
   environment	none	OTLP deployment.environment resource attribute
   resourceAttributes	{}	Extra OTLP resource attributes
   flushInterval	30s	Periodic flush interval
   flushAt	20	Buffer threshold that triggers an automatic flush
   maxBatchSize	50	Max records per outbound POST
   maxBufferSize	1000	Max records held on disk before FIFO eviction
   rateCapMaxLogs	500	Max records per rateCapWindow. Set to 0 to disable.
   rateCapWindow	10s	Rate-cap window length

   Defaults are tuned for cellular-aware mobile apps. Raise rateCapMaxLogs and maxBufferSize for high-volume scenarios.

   On web, these fields are not applied – configure them in your posthog.init({...}) call in web/index.html instead.

6. 6

   Filter or redact with beforeSend

   Optional

   Use config.logsConfig.beforeSend for redaction, sampling, or filtering by level. It is a List<BeforeSendLogCallback>, where each callback is a FutureOr<PostHogLogRecord?> Function(PostHogLogRecord). Callbacks run in Dart on all platforms (including web), evaluated left-to-right. Each callback receives a mutable PostHogLogRecord (with mutable body, level, and attributes) and returns either the (possibly mutated) record or null to drop it. Callbacks can be synchronous or asynchronous.

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   config.logsConfig.beforeSend = [
     (record) {
       // Drop debug logs in production
       if (record.level == PostHogLogSeverity.debug) return null;
   
       // Redact a sensitive attribute
       record.attributes?.remove('password');
       return record;
     },
     // Compose a chain – callbacks run left-to-right
     (record) => record.body.contains('secret') ? null : record,
   ];

   Returning null from any callback short-circuits and drops the record. Setting record.body to an empty or whitespace-only string also drops the record. A callback that throws is logged and the record is dropped (fail-closed).

7. Next steps

   Checkpoint

   What you can do with your logs

   Action	Description
   Why you need logs	What logs show you that nothing else does
   Search logs	Use the search interface to find specific log entries
   Filter by level	Filter by INFO, WARN, ERROR, etc.
   Link session replay	Connect logs to users and session replays by passing posthogDistinctId and sessionId
   Link logs to a person	Surface every log emitted on behalf of a user on their PostHog person profile
   Logging best practices	Learn what to log, how to structure logs, and patterns that make logs useful in production

   Troubleshoot common issues