Configure the logs with logback.xml, the configuration with gatling.conf, and the zip bundle command options

Gatling can be configured and optimized in three ways:

  • with configuration files, located in conf directory
  • with command line options
  • with the $JAVA_OPTS environment variable

Configuration files


This file allows you to configure the log level of Gatling. For further information, you should have a look at the Logback Documentation.


Gatling configuration is based on the great Typesafe Config library.

Gatling configuration files, such as the default configuration file, use the HOCON format.

Gatling uses a fallback strategy, where:

System properties > gatling.conf > gatling-defaults.conf

gatling-defaults.conf is shipped in the gatling-core jar and must not be tampered.

gatling.conf is the default name of the user defined file. It’s resolved from the ClassLoader, not the filesystem, meaning it must be placed in src/test/resources for a maven/gradle/sbt project and in conf in the bundle distribution.

This file name can be changed with a System property named gatling.conf.file, eg -Dgatling.conf.file=gatling-special.conf. Again, beware it’s loaded from the ClassLoader, not the filesystem, eg:

  • -Dgatling.conf.file=src/test/resource/gatling-special.conf is incorrect
  • -Dgatling.conf.file=gatling-special.conf where gatling-special.conf is placed in src/test/resource is correct

The bundle distribution and the maven/gradle/sbt plugins demo projects contain an easy-to-edit gatling.conf file with all the available properties commented with the default values.

If you want to override default values, you have two possibilities:

  • change the value in gatling.conf.
  • set a System property (the name of the property must match the HOCON Path)

Zip Bundle Command Line Options

Gatling can be started with several options listed below:

Option (short) Option (long) Description
-h --help Help
-nr --no-reports Runs simulation but does not generate reports
-ro <folderName> --reports-only <folderName> Generates the reports for the simulation log file located in <gatling_home>/results/<folderName>
-rf <path> --results-folder <path> Uses <path> as the folder where results are stored
-rsf <path> --resources-folder <path> Uses <path> as the folder where resources are stored
-sf <path> --simulations-folder <path> Uses <path> as the folder where simulations are stored
-bf <path> --binaries-folder <path> Uses <path> as the folder where simulation binaries are stored
-s <className> --simulation <className> Uses <className> as the name of the simulation to be run
-rd <description> --run-description <description> A short <description> of the run to include in the report


Default command line options for JAVA are set in the launch scripts. You can use the JAVA_OPTS environment variable to override those defaults, eg:

JAVA_OPTS="myAdditionalOption" bin/

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