Run mode will run a single workflow from the command line, and exit when the workflow completes (successfully or not). The exit code of the run command will be 0 if the workflow succeeds or is aborted, 1 if it fails.

Sending a SIGINT signal (via CTRL-C for example) will by default abort all running jobs and then exit. This behavior can be configured, and is explained in more details in the Abort section of the configuration.

Run mode is a good way to get started with Cromwell and experiment quickly. For more advanced use cases involving large workflows or multi-tenancy for example, Server mode is recommended. It also offers a larger set of features through its endpoints that are not available in run mode.


Server mode will start Cromwell as a web server that exposes REST endpoints. By default the server will be accessible at http://localhost:8000. See the Server Section of the configuration for more information on how to configure it.

A description of those endpoints can be found in the API Section.

Follow the Server Tutorial to get your Cromwell server up and running in a few steps !