Structurizr

Structurizr is a models-as-code tool for building software architecture diagrams from a shared C4 model. It suits development teams that want consistent architecture views and developer-oriented export options; teams after a general-purpose drawing canvas should look elsewhere.

Overview

With Structurizr DSL, a team can describe a system once and produce landscape, context, container, component, code, dynamic, deployment, custom, filtered, and image diagrams. Reusing a model is a practical advantage when several views need to reflect the same architecture. It is a narrower choice than a general diagramming tool, however: its core purpose is software architecture modeling.

Workspaces can be imported in Structurizr DSL or Structurizr JSON, and version history is supported. The toolset includes a browser playground, local diagram viewer and layout editor, a self-hosted server, and a CLI export tool. A separate free, open-source MCP server can parse and validate DSL, export diagrams to PlantUML and Mermaid, and manage server-hosted workspaces.

Key features

C4 diagrams are interactive, animatable, and embeddable, and each gets an automatically generated key or legend. This makes views more useful for presenting and sharing architecture without requiring a team to maintain a legend separately.

The CLI exports workspace views as PlantUML, Mermaid, or a static HTML site. Those formats give teams options for carrying diagrams into other documentation and developer workflows. Integration options described for the CLI include GitHub Actions, GitLab CI, Homebrew, Scoop, and a Gradle plugin.

Paid cloud workspaces can use a Slack integration for full-text searches across one workspace, returning up to 10 results. For cloud security, Structurizr says data is encrypted with AES using a 128-bit key, random salt, and server-side passphrase; paid workspaces can also use client-side encryption. The cloud service runs in AWS US-East-1, stores data in RDS and S3 there, and uses HTTPS for browser and API interactions. Organizations requiring a signed Section 889 compliance form should note that Structurizr says it cannot provide one because it cannot verify its entire supply chain.

Pricing

Structurizr offers a 14-day trial and a free self-hosted server open core, built from source. That free server has no authentication and its workspaces are public, making it unsuitable for private, controlled team use.

Prebuilt self-hosted server licenses add authentication options, including SAML and LDAP on request, role-based access, sharing links, and an admin API. Pricing is per server installation, based on unique users in a one-year period; the vendor says it does not currently enforce the user limit. Support for server licenses is through the GitHub issue tracker.

• Self-hosted server, 1–20 unique users: £300 per year, billed £300 per month, billed annually and non-renewing.
• Self-hosted server, 21–50 unique users: £600 per year, billed £600 per month, billed annually and non-renewing.
• Self-hosted server, 51–100 unique users: £900 per year, billed £900 per month, billed annually and non-renewing.
• Self-hosted server, 101–250 unique users: £1,200 per year, billed £1,200 per month, billed annually and non-renewing.

The cloud server-license bands start at £300 a month for 1–20 unique users and rise to £600.00 GBP for 21–50, £900.00 GBP for 51–100, £1,200.00 GBP for 101–250, £1,500.00 GBP for 251–500, £1,800.00 GBP for 501–1000, and £2,400.00 GBP for 1001+ unique users; each is billed annually and applies per server installation. These per-installation bands make the cost scale with the user bracket, so teams should match the tier to their annual unique-user count rather than treating it as a per-seat subscription.

Platforms

Structurizr supports web, API, Linux, macOS, Windows, and self-hosted use. The mix accommodates teams working in a browser, through tooling, or on their own server.

Who it's for

Structurizr is best suited to software teams that want a shared C4 model to drive multiple architecture views, with export formats and developer integrations to support documentation workflows. It is less suitable for people who need a broad diagramming canvas, or organizations that require Section 889 compliance forms.

Pros and cons

• Pro: One model supports many architecture views, helping keep related diagrams aligned.
• Pro: Interactive, animatable, embeddable diagrams and automatic legends support clearer sharing and presentation.
• Pro: CLI exports to PlantUML, Mermaid, and static HTML provide practical routes into other documentation formats.
• Con: The free self-hosted server has no authentication and public workspaces, so it does not suit private team workspaces.
• Con: Paid server licenses are priced per installation and user band, with the lowest listed cloud band at £300 a month, billed annually.
• Con: Structurizr cannot sign Section 889 compliance forms, which rules it out for organizations that require them.

Alternatives

For a conventional, free diagramming option with web, desktop, and mobile platforms, consider draw.io; its free plan requires no sign-up or credit card. EdrawMax is another freemium diagramming alternative, with a free plan that includes 500 AI tokens, 100M cloud storage, and limited Visio, SVG, and CAD import.

Sparx Enterprise Architect is worth considering for a UML modeling environment with multi-user projects and code engineering. Creately offers a free plan with unlimited canvases and collaborators, capped at 45 items per canvas.

Eclipse Papyrus is a free, open-source modeling environment with no usage limits stated. Lucidchart may suit teams wanting a visual diagramming service, though its free tier is limited to three editable documents, 60 shapes per document, and 100 basic templates.

Mermaid is a free choice for diagramming through a developer-oriented platform, while its Basic plan is limited to six diagrams and a diagram size of 60. Microsoft Visio is a paid alternative with a web, Windows, and macOS footprint; its Visio Plan 1 starts at $5 a month on an annual subscription that auto-renews.

For broader discovery, browse Diagram Software and Diagramming Software.

Verdict

Choose Structurizr if your team wants C4 architecture views derived from one model and values export paths into developer documentation workflows. Its model reuse and diagram capabilities are compelling for that focused job; the main reason to look elsewhere is the cost of private, access-controlled server deployment or the need for a broader canvas or compliance form.