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What's New


  • --app and --channel parameters are now optional. If a command needs them and you haven't specified them, then it will error.
  • list and fetch-list now have filters. You can filter on slug, feature, is-rollout, active-on date, and enroll date.
  • --patch FILE is now available for any command which accepts an experiment.
  • start-server – a new command to start a web server, which devices can connect to. Firefox for iOS and Android support this from v117.
    • pbcopy adds to the clipboard a URL with experiments encoded in them.
    • pbpaste sends the URL to the server. In this way, we can open enroll apps on device into experiments with the CLI.
  • fml – a new command to interact with the lower level nimbus-fml command line.


  • Now using the Experimenter API to get experiments, instead of Remote Settings. This saves time waiting for the sync between Experimenter and RS.
  • Split fetch into a fetch for named recipes and fetch-list for getting a list; this changes the parameters for fetch.
  • Passthrough parameters for finer control of the app launch process. Thanks Ben, for the suggestion.
  • A new features command to get the feature configuration out of the experiment. You can also merge with the defaults from the manifest.
  • A new defaults command to get the defaults from the manifest.
  • A new info command to get information about the experiment. This can be good for investigations.
  • Experiment slugs can be derived from Experimenter URLs.
  • Where you can read and write JSON, you can now read and write YAML.