Structurizr

Structurizr is a models-as-code tool for teams documenting software architecture with C4 diagrams. It is best suited to developers who want multiple views of a system to stay anchored to one model. Its export and deployment options are useful, but private self-hosting with access controls comes at a per-installation license cost.

Overview

Write an architecture model in Structurizr DSL, then use it to create system landscape, system context, container, component, code, dynamic, deployment, custom, filtered, and image diagrams. This shared-model approach helps keep related views consistent as a system changes; it is less compelling for people who mainly need an open-ended canvas for unrelated diagrams. Workspaces can be imported as Structurizr DSL or Structurizr JSON, and version history is supported.

The toolkit includes a browser playground, a local diagram viewer and layout editor, a self-hosted server, and a command-line export tool. A separate free, open-source MCP server can parse and validate DSL, export to PlantUML and Mermaid, and manage server-hosted workspaces.

Key features

C4 diagrams are interactive, animatable, and embeddable, with an automatically generated key or legend. These touches make architecture views easier to present and share without requiring teams to maintain a legend for each diagram.

The CLI can export workspace views to PlantUML, Mermaid, or a static HTML site, giving developer workflows a route to formats beyond Structurizr itself. Documentation describes integration options for GitHub Actions, GitLab CI, Homebrew, Scoop, and a Gradle plugin. Paid cloud users also get a Slack integration for slash-command full-text searches across one workspace, returning up to 10 results.

The cloud service uses HTTPS for browser and API interactions and says workspace data is encrypted with AES using a 128-bit key, random salt, and server-side passphrase. Paid workspaces can use client-side encryption. Cloud data is hosted in AWS US-East-1 and stored in RDS and S3 there, which may not suit organizations with different residency requirements. Structurizr cannot sign Section 889 compliance forms because it cannot verify its entire supply chain.

Pricing

Structurizr has a free plan, a 14-day trial, and paid licensing. The self-hosted server open core costs nothing when built from source, but has no authentication and makes workspaces public. That is a meaningful constraint for private team architecture; it is best reserved for public workspaces or setups that can accept those limits.

Paid prebuilt server binaries add authentication options, role-based access, sharing links, and an admin API. Licenses apply to each server installation and are priced by unique users in a one-year period. The vendor says it does not currently enforce the user limit. Annual, non-renewing server licenses are:

• 1–20 unique users: £300 a year, billed £300 per month
• 21–50 unique users: £600 a year, billed £600 per month
• 51–100 unique users: £900 a year, billed £900 per month
• 101–250 unique users: £1,200 a year, billed £1,200 per month

Higher server tiers are £900 a month for 51–100 unique users, £1,200 a month for 101–250, £1,500 a month for 251–500, £1,800 a month for 501–1000, and £2,400 a month for 1001+; each is billed annually and applies per server installation. Support for server licenses is available through the GitHub issue tracker. These costs make the paid server a better fit for organizations that need private, access-controlled hosting than for small teams seeking an inexpensive standalone diagram editor.

Platforms

Structurizr supports API, Linux, macOS, self-hosted, web, and Windows. The mix accommodates browser-based work as well as local tools and server deployments.

Who it's for

Choose Structurizr if software architects and development teams need a model-driven set of C4 views, want diagrams to travel through developer workflows, or need export paths to PlantUML, Mermaid, or static HTML. It is a weaker fit for users who want a broad, general-purpose diagram canvas, or for organizations that require Section 889 compliance forms or cloud storage outside AWS US-East-1.

Pros and cons

• Pro: One DSL model can drive a broad range of architecture views, helping teams keep related diagrams aligned.
• Pro: CLI exports, developer integration options, and the MCP server provide several ways to connect architecture work with software workflows.
• Pro: Interactive, animatable, embeddable diagrams with auto-generated legends are presentation-friendly.
• Con: The free self-hosted open core has no authentication and public workspaces, making it unsuitable for private collaboration without a paid license.
• Con: Server licensing is charged per installation and scales by annual unique-user band, which can raise costs for larger deployments.
• Con: Cloud hosting is in AWS US-East-1, and the vendor cannot sign Section 889 compliance forms.

Alternatives

draw.io is worth choosing instead for a free, open-source diagramming tool with no sign-up required and support for web, desktop, and mobile platforms. For users who want a freemium option with a free tier offering unlimited canvases and collaborators, Creately is another alternative, though its free canvases are limited to 45 items each. Mermaid suits readers looking for a free diagramming option whose basic plan allows up to six diagrams and has a diagram-size limit of 60.

PlantUML is an alternative free, open-source choice. EdrawMax offers a freemium alternative with a free tier that includes 500 AI tokens and 100M cloud storage. Sparx Enterprise Architect is another freemium alternative, while Microsoft Visio is a paid option with a plan starting at $5 a month, paid yearly. Archi is also available as free, open-source software for Linux, macOS, and Windows. Browse Diagram Software or Diagramming Software for more options.

Verdict

Structurizr is a strong choice for software teams that want a shared C4 model to generate and export multiple architecture views. The model-driven workflow is its central advantage; the main reason to look elsewhere is the cost of private, access-controlled self-hosting, alongside cloud or compliance constraints that do not fit an organization’s requirements.