Open Source Enterprise Architecture Tools: 10 Free Options for 2026

Most teams searching for open source enterprise architecture tools are in the same spot: they want an EA practice, or just one shared model of the estate, without signing a commercial license first. Two names keep coming up: Archi, the MIT-licensed ArchiMate modeler, and Essential Open Source, an EA repository licensed under GPL or AGPL. Neither is the whole answer.

Open source means the code ships under an OSI-approved license that lets you inspect it, change it, and host it yourself; free often just means a proprietary product costs nothing to use. Below we map free enterprise architecture tools by what they are (modeler, repository, or architecture as code), check each license at the source, and cover what it takes to install, host, and keep the model current. Paid suites are in our full enterprise architecture tools comparison.

What Counts as an Open Source Enterprise Architecture Tool?

An open source enterprise architecture tool is software for modeling or storing how an organization fits together: capabilities, applications, data flows, and technology. It ships under an OSI-approved open source license, so you can read the code, modify it, and self-host it, and the category covers ArchiMate and UML modelers, EA repositories, and architecture-as-code tooling.

If you only need a starting point, pick by job:

• Archi for ArchiMate modeling on a desktop. Main limitation: a model is a local file until you add a Git server and the coArchi plug-in.
• Essential Open Source for a governed EA repository. Main limitation: a multi-user install typically takes 3 to 6 hours, and there are no APIs.
• Structurizr for C4 diagrams written as code. Main limitation: it's built around C4 and software architecture, with no ready-made model for business capabilities.

Open Source vs. Free vs. Community Edition

Three kinds of "free" show up in this category, and they behave differently once you depend on them:

• Open source tools ship under an OSI-approved license that lets you inspect, modify, and run the code yourself, like Archi (MIT) or Modelio (GPL v3).
• Free proprietary tools, like Sparx Enterprise Architect Lite, cost nothing but give you no source.
• Community editions, like ADOIT Community Edition, are vendor-hosted free versions of a commercial product with a built-in upgrade path.

Check the license file yourself: EA Design It calls itself open source but ships without a license (more on that below).

Modeling Tool or Architecture Repository?

A modeler such as Archi or Modelio is a drawing surface with rules: you build views in ArchiMate, UML or BPMN, and the tool keeps the elements behind them consistent. A repository works the other way round. In Essential, diagrams, dashboards and reports are generated from the enterprise information and relationships held in one governed repository. That suits portfolio questions like "which applications depend on this database?", but someone has to keep feeding it.

Architecture as code is a third shape: text files in Git that generate views. All three depend on someone keeping the model current, by hand or through imports and scripts the team maintains, which is the line we draw when explaining what an enterprise architecture platform is.

Open Source Enterprise Architecture Tools Compared

For each tool, we checked the LICENSE file or license page, the latest release, the install docs, and the claimed standards as of October 2026. We also looked at what it takes to run for a team, not one person. Catio isn't on the list because it's neither open source nor free (although we do offer a free trial to get you started!).

Archi

It's an MIT-licensed modeler for ArchiMate 3.2, written in Java on the Eclipse Rich Client Platform, so it runs on Windows, macOS, and most Linux distros. Version 5.10.0 shipped on September 3, 2026, and still targets ArchiMate 3.2, while The Open Group released ArchiMate 4 in April 2026.

The costs appear when a second architect joins, because by default a model is a file on someone's laptop. Shared editing comes from the coArchi plug-in, which versions models in a Git repository on a Git server you run. Its rewrite, coArchi2, is still a work in progress, with early access for Patreon supporters. None of that is expensive, but somebody owns the Git server.

Essential Open Source

Essential Open Source provides a self-hosted EA repository without a license fee. It's licensed under GPL v3 (or later) or AGPL v3, depending on the release.

You get a shared repository with around 140 visualizations and Excel import, which suits capability maps and application portfolio management, but running it is a small project. The single-user "Essential in a Box" build (V6.21.1, released October 15, 2025) is fine for evaluation but not for multi-user work. A team install needs Java 1.8, the Essential Protege ontology editor, and Tomcat 8.5 or 9.0, optionally backed by MySQL, Postgres, or SQL Server. The project typically takes 3 to 6 hours to install.

With the open source edition, you get basic data capture and community support, but no APIs; your team also owns updates. Entering data also requires understanding Essential's meta-model.

Modelio

If your team thinks in UML first and wants ArchiMate in the same tool, look at Modelio. It's GPL v3 and covers UML, BPMN, SysML, and TOGAF, with ArchiMate as a downloadable extension and XMI import and export for moving models between tools.

Modelio 6.2 is available with Windows and Linux packages, while the project website still promotes 5.4.1. Use the GitHub releases and version-specific release notes to evaluate the build you plan to deploy rather than relying on the website headline. The visible release listing jumps from 5.4.1 to 6.2; that gap alone doesn't show how much development happened between them.

Gaphor

Gaphor has no ArchiMate support and no shared repository, so it complements an EA tool rather than replacing one. It fits best for solution-level modeling around one system. It's an Apache 2.0 modeler written in Python, with templates for UML, SysML, RAAML, and the C4 model. The project describes its underlying UML 2 data model as fully compliant, and version 3.3.2 shipped on May 2, 2026.

EA Design It

EA Design It is a small self-hosted web app (Java, Spring Boot and Vue.js on JHipster, shipped as a Docker image) that treats architecture as a database of applications, interfaces and flows. Excel import/export and an API let you populate the repository from existing data and your own scripts. It also generates PlantUML component diagrams and draw.io landscapes that keep your layout when a new application appears.

Check two things before you rely on it. The latest release (v1.1.2) and latest commit both date from April 23, 2024. And although the README calls it open source, the repository has no LICENSE file, and its package.json declares "UNLICENSED". Per GitHub's own guidance, code without a license falls under default copyright: other GitHub users can view and fork it, but nobody may reproduce, distribute, or create derivative works from it. Get written permission from the author before building on it.

Open Source Architecture as Code and Diagramming Tools to Pair With Them

Architecture as code isn't EA in the TOGAF sense, and it overlaps with the wider field of software architecture tools. Still, plenty of teams searching for open source EA tools want a model engineers will keep current, which usually means text in Git.

Structurizr and the C4 Model

With Structurizr, you write a C4 model once in the Structurizr DSL and generate multiple diagrams from it. The model is plain text, so it versions in Git like any other file. Its open source boundaries have shifted recently, so distinguish the source license from the commands and binaries you plan to run:

• The main Structurizr repository is Apache 2.0, latest release 2026.09.19.
• The free, open-source local command replaces Structurizr Lite for viewing diagrams on your own machine.
• The server command has an open core that's free when you build it from source; prebuilt binaries add enterprise features such as SAML and role-based access and require a license.
• Structurizr Lite, the on-premises edition, the standalone CLI, and the hosted cloud service are listed as end-of-life.

For a team, that means a self-built server with no authentication, or a license.

FINOS CALM

CALM earns its place when you want architecture definitions that tooling can check, rather than pictures people interpret. The Common Architecture Language Model is an Apache 2.0 specification from the Fintech Open Source Foundation (FINOS), with a CLI and other tooling around it. Architecture definitions use a common machine-readable format that you can keep under version control. It's still incubating, so expect the spec and tooling to change. Our architecture as code primer covers CALM alongside Structurizr and the other approaches.

PlantUML, Mermaid and diagrams.net

PlantUML is offered under several licenses (GPL, LGPL, Apache 2.0, MIT and others), Mermaid is MIT, and the diagrams.net source is Apache 2.0. They're good for views inside a README or an ADR. None is a system of record, though: nothing stops two diagrams from disagreeing about the same service, and no query tells you which applications touch a given database.

Free Enterprise Architecture Tools That Are Not Open Source

Several free enterprise architecture tools are proprietary, and some "free" EA listings turn out to be trials or paid tiers. Essential Cloud, the hosted edition of Essential, is commercially licensed, and Essential's pricing page lists it from US$24,999 a year. Check the current plan and any optional charges before you budget.

ADOIT Community Edition

There's nothing to install with ADOIT Community Edition, and that's most of its appeal: it's BOC Group's free, cloud-hosted edition of its commercial ADOIT platform. You can start in ArchiMate Lite mode or use full ArchiMate 3.1, import models from Excel, and connect through REST APIs. BOC lists it as TOGAF-certified. Support comes from the community rather than the vendor's support desk. The trade-offs are that your model lives in a vendor's cloud, and BOC markets its paid Enterprise Edition as the multi-user one.

Sparx Enterprise Architect Lite

Sparx Enterprise Architect Lite only makes sense if someone on the team already models in paid Sparx EA and sponsors need to browse without buying seats. It's a free, read-only Windows viewer for those models, with editing and document generation disabled.

How to Choose a Free or Open Source EA Tool

Answer these six questions before you install anything, especially if you're starting an EA practice from scratch:

Where Open Source EA Tools Stop (and What Fills the Gap)

Every tool on this list costs nothing to start with, and not one of them keeps itself current. Archi's model is whatever the last person saved; Essential's open source edition has no APIs and only simplistic data capture, and architecture-as-code files stay current only while engineers edit them or maintain the scripts that generate them. For a team learning ArchiMate or running a small EA practice, that's a fair trade, and Archi or Essential may be all you need.

It stops being fair when the questions are about the running system: what actually calls this service, how the current state differs from the last review, whether a planned migration still fits what's deployed. That's the problem we built Catio for. Instead of a model someone transcribes, Stacks in our Architecture IDE builds diagrams from the integrations you connect, such as AWS, GitHub source code, Kubernetes, and VPC Flow Logs. What you see is the system as it runs now, within what those integrations cover. Our homepage puts the time to a decision-grade system view at five minutes.

Archie, our reasoning agent, sits on that model so you can ask about your architecture and weigh trade-offs in plain language instead of building a custom report. Flagging drift between the running system and the intended design is the part we're still rolling out.

Today we cover AWS estates at companies past the early-stage startup phase, and Catio isn't free: there's a two-week trial, then paid plans. And despite the name, the Architecture IDE doesn't replace coding IDEs; it defines what they execute. The Catio MCP is how that works in practice: it pulls committed designs and architecture context into Claude Code, Cursor, and other MCP-capable editors.

We do contribute on the open source side. GraphQA is our Apache 2.0 agent for asking natural-language questions of a graph, built on NetworkX and labeled research/experimental software. It isn't an EA tool, and it needs an OpenAI API key, but it's a quick way to poke at dependency data.

When It Is Time to Move to a Commercial EA Platform

Three signals usually mean the free path has run out:

1. The model is consistently behind the estate, and the team spends more time updating it than using it.
2. Several people need to edit with permissions and an audit trail, and nobody wants to own a Tomcat server or Git workflow to get there.
3. Stakeholders expect impact analysis and roadmaps on demand, not a quarterly deck.

At that point you're comparing paid platforms such as LeanIX, Ardoq and Catio, which we cover side by side in our full enterprise architecture tools comparison.

Conclusion

If you need ArchiMate views, start with Archi. If you need a shared repository and can spare a few hours of setup plus someone to feed it, install Essential Open Source. If your architects live in Git, Structurizr and CALM keep the model next to the code. Whichever you choose, budget for upkeep, because a model nobody updates stops being consulted.

When your model can't keep pace with an AWS estate, sign up for Catio and use it to investigate one architecture question on your own system, starting from what's actually running.

Frequently Asked Questions

Is there a free architecture software?

Yes. Archi, Essential Open Source, Modelio and Gaphor are open source and free, while ADOIT Community Edition and Sparx EA Lite are free proprietary options. Your costs are hosting, multi-user setup, and keeping the model current.

Is ArchiMate still relevant?

Yes. The Open Group released the ArchiMate 4 Specification in April 2026, cutting the element types from a bit more than 60 to 40 to make the language easier to learn. Tools are still catching up: Archi 5.10.0, released September 3, 2026, supports ArchiMate 3.2, and ADOIT Community Edition lists 3.1. It pays off when business and IT need one shared notation; engineering-only teams often get further with C4.

What are the top 5 enterprise architecture tools?

It depends on budget, so we'll answer for the free side: our shortlist is Archi, Essential Open Source, Modelio, Structurizr, and ADOIT Community Edition. For paid platforms, see our full enterprise architecture tools comparison.

Is there an open source alternative to Sparx Enterprise Architect?

Archi is an option for ArchiMate modeling. Modelio is closer in breadth because it covers UML, BPMN, SysML, and ArchiMate in one tool, so list the diagram types you actually use before you switch.

What is the best free tool to create an architecture diagram?

For quick drag-and-drop diagrams, diagrams.net is the usual starting point; Mermaid or PlantUML suit teams that want diagrams as text in Git. For C4 diagrams generated from one model, Structurizr's free local command does the job.