The Structurizr tooling is available in a number of versions, covering different usage scenarios.
See Documentation - Products for a comparison.
The Structurizr cloud service (structurizr.com) provides an easy way to publish diagrams, documentation, and architecture decision records.
Free and paid subscriptions
A self-hosted version of Structurizr that can be run on your own infrastructure (local servers or cloud), with a variety of data storage and SSO options.
Open source
A standalone version of Structurizr designed for individual/local authoring.
Open source
Recommended starting point
A command line utility designed to be used in conjunction with the Structurizr DSL, supporting pull/push via the cloud service/on-premises web APIs plus exports to a number of "diagrams as code" formats including PlantUML and Mermaid.
Open source
Rendering tool independent
In addition to the browser-based diagram renderer of the Structurizr cloud service/on-premises installation/Lite, the open source structurizr-export library (built-in to the Structurizr CLI) can export your views to a number of other formats, for visualising with other tools. Other rendering tools are available too; see Structurizr - Community tooling for more.