Extensible logging for Dart and Flutter.

Package is based on famous Android logging library API - Timber, this is library for simplify logging for Flutter. Using similar (as far as Dart lang allows) method API with same concepts for tree and planting logging tree. Also check out flutter_fimber which extends fimber to platform specific output and logging style.

Getting Started

To start add using it:

Add fimber to pubspec.yaml


  fimber: ^0.7.0
  • remember about import in file you plan to use Fimber
import 'package:fimber/fimber.dart';

Initialize logging tree on start of your application

void main() {
  // app code here ...
  // DebugTree options for time elapsed
  // by default DebugTree will output timestamp of the VM/Flutter app
  // to enable elapsed time since planting the tree log

Remove a tree from logging

If the Tree implements UnPlantableTree interface, its methods will be called.

void main() {
  var myDebugTree = DebugTree();


  /// Do something



### Start using it with static methods:

import 'fimber.dart';

void main() {
  var parameter = 343.0;
  // use directly
  Fimber.i("Test message $argument");
  Fimber.i("Extra error message", ex: Exception("Test thorwable"));
  // other log levels
  try {
    throw Exception("Exception thrown");
  } catch (e, stacktrace) {
    // providing `stacktrace` will better show where issue was thrown
    // if not provided will use log line location.
    Fimber.i("Error caught.", ex: e, stacktrace: stacktrace);

This will log the value and grab a TAG from stacktrace - that is little costly and if more logs will be done per second.

Colorize logs - ColorizeStyle

useColors property set to true will use default colors of the logos, you can change the mapping with in colorizeMap for DebugTree and CustomFormatTree The useColors by default is disabled.

ColorizeStyle Aggregates list of AnsiStyle so you can combine styles together.

AnsiStyle is combination of AnsiColor and AnsiSelection values

Here is output of test output.

Colorize Test Output

CustomFormatTree format your line of code

Use any of the Tokens at CustomFormatTree class to configure the log lines.

more at file

  /// Format token for time stamp
  static const String timeStampToken = "{TIME_STAMP}";

  /// Format token for time elapsed
  static const String timeElapsedToken = "{TIME_ELAPSED}";

  /// Format token for log level character
  static const String levelToken = "{LEVEL}";

  /// Format token for log tag
  static const String tagToken = "{TAG}";

  /// Format token for main log message
  static const String messageToken = "{MESSAGE}";

  /// Format token for exception message
  static const String exceptionMsgToken = "{EX_MSG}";

  /// Format token for exception's stacktrace
  static const String exceptionStackToken = "{EX_STACK}";

  /// Format token for file path.
  static const String filePathToken = "{FILE_PATH}";

  /// Format token for file name.
  static const String fileNameToken = "{FILE_NAME}";

  /// Format token for file's line number
  static const String lineNumberToken = "{LINE_NUMBER}";

  /// Format token for character index on the line
  static const String charAtIndexToken = "{CHAR_INDEX}";

Create tagged version of Fimber

And use its instance inside class, you can create logger for a dart file or for a class.

var logger = FimberLog("MY_TAG");

void main() {
  logger.d("Test message");

// or inside a class
class SomeBloc {
  var logger = FimberLog("SomeBloc");
  String fetchMessage() {
    logger.d("About to fetch some data.");
    var data = "load something";

    logger.d("Retrived data (len = ${data.length}");
    return data;

Use block function and pass method that uses logger.

Use this function to log multiple messages with same tag, allows optional return value. Due to nature of auto-tag generation from stacktrace this block only does it once and create local FimberLog instance to pass into the anonymous method.

    var someMessage = "Test message from inside of block";
    var output = Fimber.block((log) {
      log.d("Started block");
      var i = 0;
      for (i = 0; i < 10; i++) {
        log.d("$someMessage, value: $i");
      log.i("End of block");
      return i;

Deprecated moved to fimber_io package

Custom line formatters

Use custom line formatters to define your logging format.

import 'package:fimber_io/fimber_io.dart';


        logFormat: "${CustomFormatTree.timeElapsedToken} ${CustomFormatTree
            .messageToken} ${CustomFormatTree.timeStampToken}"

Use file log tree - the logs will go to a log file (Useful in DartVM apps). There are log rolling with size and time/date interval, so it is possible to setup log output per hour/day or any other time.

see: SizeRollingFileTree or TimedRollingFileTree or use abstract class RollingFileTree to create your own version of rolling log file.

TODO - road map


   Copyright 2018 Mateusz Perlak

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   See the License for the specific language governing permissions and
   limitations under the License.