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Getting Started

Just create an instance of Logger and start logging:

var logger = Logger();

logger.d("Logger is working!");

Instead of a string message, you can also pass other objects like List, Map or Set.


Log level

You can log with different levels:

logger.v("Verbose log");

logger.d("Debug log");

logger.i("Info log");

logger.w("Warning log");

logger.e("Error log");

logger.wtf("What a terrible failure log");

To show only specific log levels, you can set:

Logger.level = Level.warning;

This hides all verbose, debug and info log events.


When creating a logger, you can pass some options:

var logger = Logger(
  filter: null, // Use the default LogFilter (-> only log in debug mode)
  printer: PrettyPrinter(), // Use the PrettyPrinter to format and print log
  output: null, // Use the default LogOutput (-> send everything to console)

If you use the PrettyPrinter, there are more options:

var logger = Logger(
  printer: PrettyPrinter(
    methodCount: 2, // number of method calls to be displayed
    errorMethodCount: 8, // number of method calls if stacktrace is provided
    lineLength: 120, // width of the output
    colors: true, // Colorful log messages
    printEmojis: true, // Print an emoji for each log message
    printTime: false // Should each log print contain a timestamp

Auto detecting

With the io package you can auto detect the lineLength and colors arguments. Assuming you have imported the io package with import 'dart:io' as io; you can auto detect colors with io.stdout.supportsAnsiEscapes and lineLength with io.stdout.terminalColumns.

You should probably do this unless there's a good reason you don't want to import io, for example when using this library on the web.


The LogFilter decides which log events should be shown and which don't.
The default implementation (DevelopmentFilter) shows all logs with level >= Logger.level while in debug mode. In release mode all logs are omitted.

You can create your own LogFilter like this:

class MyFilter extends LogFilter {
  bool shouldLog(LogEvent event) {
    return true;

This will show all logs even in release mode. (NOT a good idea)


The LogPrinter creates and formats the output, which is then sent to the LogOutput.
You can implement your own LogPrinter. This gives you maximum flexibility.

A very basic printer could look like this:

class MyPrinter extends LogPrinter {
  List<String> log(LogEvent event) {
    return [event.message];

If you created a cool LogPrinter which might be helpful to others, feel free to open a pull request. :)


Please note that all IDEs (VSCode, XCode, Android Studio, IntelliJ) do not support ANSI escape sequences in their terminal outputs. These escape sequences are used to color output. If using such an IDE do not configure colored output.

However, if you are using a JetBrains IDE (Android Studio, IntelliJ, etc.) you can make use of the Grep Console Plugin and the PrefixPrinter decorator to achieved colored logs for any logger:

var logger = Logger(
  printer: PrefixPrinter(PrettyPrinter(colors: false))


LogOutput sends the log lines to the desired destination.
The default implementation (ConsoleOutput) send every line to the system console.

class ConsoleOutput extends LogOutput {
  void output(OutputEvent event) {
    for (var line in event.lines) {

Possible future LogOutputs could send to a file, firebase or to Logcat. Feel free to open pull requests.


Small, easy to use and extensible logger which prints beautiful logs.