-This page describes how to set up the runtime environment (e.g., the programs, libraries, and other dependencies needed to run a job) that a workflow step will be run in using "Docker.":https://www.docker.com/ Docker is a tool for building and running containers that isolate applications from other applications running on the same node. For detailed information about Docker, see the "Docker User Guide.":https://docs.docker.com/userguide/
+This page describes how to set up the runtime environment (e.g., the programs, libraries, and other dependencies needed to run a job) that a workflow step will be run in using "Docker":https://www.docker.com/ or "Singularity":https://sylabs.io/singularity/. Docker and Singularity are tools for building and running containers that isolate applications from other applications running on the same node. For detailed information, see the "Docker User Guide":https://docs.docker.com/userguide/ and the "Introduction to Singularity":https://sylabs.io/guides/3.5/user-guide/introduction.html.
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+Note that Arvados always works with Docker images, even when it is configured to use Singularity to run containers. There are some differences between the two runtimes that can affect your containers. See the "Singularity architecture":{{site.baseurl}}/architecture/singularity.html page for details.