6 UML tools for every occasion

Unified Modelling Language (UML) abstracts and visualises systems of object-orientated programming. This makes the modelling language a practical tool for developers: On the one hand, it makes it possible to create clear blueprints for software projects, on the other hand, complex software systems can also be presented in an understandable way for people not familiar with the subject. For example, if you want to introduce new software for the latest company app to the Head of Marketing, do not use code – instead, you can use UML to show them the most important features of the app.

UML diagrams obviously aren’t drawn using Paint. UML tools are used to help you with the modelling language, but finding the right tool is not that easy. There are countless providers of UML programs on the net, but not every program offers the same functions. While some tools require less memory, they have few features. Other UML diagram tools can map any diagram type and export it to different programming languages and import a model from existing code. In return, many programs like these do not offer any function to exchange information about projects in a team.

The Object Management Group (OMG for short), specifies the UML standard – so you first should consider what you want to represent with UML. Should the system’s structure be shown or the system behaviour? Depending on the answer, you then choose a UML tool that is suitable for your project.

This article was last updated in May 2021.

Whether free UML tool, online UML tool, or integrated development environment, the best UML tool is one that performs the desired tasks efficiently and uses as few resources as possible. As you can see from the previous list, there are UML tools of every colour. Whether you want to make a quick draft or create source code frames for a complex system and analyse them using diagrams – one of these applications will certainly be able to help you. Since nobody wants to spend the entire monthly budget on a tool for creating drafts, we have also considered the prices for individual offers in our comparison. In the following overview, we summarise the most important key features of UML diagram tools.

Unified-Modeling-Language specifies 14 diagram types that represent the structure, behaviour, and interactions of a system. To work with this language, you need the right tool – UML tools are modelling tools that can do much more than simple drawing tools. These programs do not only provide the standardised UML shapes, which can be provided with corresponding arrows and labels, but they are often platform-independent and export your UML diagrams in various formats. With some, you can also import code and display it as a diagram – or export diagrams as a code template. Other tools allow you to specify UML independently to create profiles that fit your project.

Depending on how far along you are with your project, particular tools might be more suited than others. Therefore, it makes sense to have more than one program at hand. These do not necessarily have to be desktop apps - there are also a variety of online UML tools. Although these often have a smaller range of functions, they are perfectly sufficient for making quick first drafts. It is important for the program to export your diagram via XMI (short for XML Metadata Interchange) in a format that is compatible with your other tools. In the following few paragraphs, we will explain some use cases and give tips on which functions a UML tool should offer in each case.

Are you still at the beginning and only have a few initial ideas for the structure? Or do you want to quickly display a part of the system graphically? Then free UML tools are an effective solution. If you are in a hurry, just grab a pen and paper or use a simple drawing tool. However, these variants can never be more than simple sketches and that’s it. A free UML tool would attribute meaning to these drawings. For example, a simple rectangle with the label <<classifier>> symbolises the instance of a class.

If you’re working in a team and the draft becomes a usable prototype, a UML tool enables you to export the diagram to a more feature-rich program via XMI. There you can integrate it into your existing architecture or extend the model you have just created. When choosing a UML tool, ask yourself the following questions:

• Do I want to program based on this graphic?
• Is the system area that I want to illustrate very complex?
• Do I have much time to familiarise myself with the program?
• If you answered ‘no’ to most of these questions, you should select a program that …

• Works fast.
• Doesn’t offer any superfluous functions, but only models the diagrams you need.
• Is a user-friendly, intuitively understandable user interface.
• Is available free of charge.
• Is a web application so you don’t have to download a new program.

The main task of UML is to simplify complex systems, making them understandable even for beginners. A good UML tool also makes teamwork and cooperation between different departments a lot easier. Since extensive tools like these are rarely free, you should make sure that they are compatible with the current version of UML 2, since UML 2 offers more diagram types than UML 1 and allows you to create profiles that metamodelling is able to tailor more precisely to your needs.

For the above use case, you need a UML diagram tool with the following features:

• It is platform-independent and ideally backwards compatible.
• The current UML diagram types are positioned at a central point in a clear menu – with all the necessary designs.
• Diagrams can be created with the drag-and-drop function, keyboard input, or imported code.
• The program should support the import and export of whichever programming language you use.
• The documentation is automatically created in the background by the program.
• Even if an error occurs in the system, the program should still be easy to use: usability and robustness are particularly important for large-scale projects with numerous users.
• Sharing and simultaneously working on a project should (if not anchored in the tool) at least work through integration with teamwork applications.
• A debugger immediately reports if errors occur in the model.
• Different perspectives for viewing as well as detailed model types provide an overview of the entire system and specific aspects.
• The tool allows simulations to eliminate error sources.

Some UML tools enable diagrams to be converted into a given programming language. They often work with Java, C++, C#, or XML schemas. Some tools also reconstruct UML diagrams from existing code. However, paradoxically, some of these tools do not necessarily provide the reverse engineering function for the same programming languages that they use to create code from UML diagrams.

If you want to convert finished source code from a UML diagram, consider how complex your application should ultimately be. Anyone that’s worked with modelling software knows how long it takes to sketch a diagram. A tool that is extensive as well as quick would be perfect for a task like this, and UML is supposed to simplify complex systems. An overly detailed and time-consuming diagram contradicts this purpose. Creating a diagram that visualises all instances, including their dependencies in detail, requires more work than simply giving a programmer team an overview and letting them get on with it.

UML diagram tools with round-trip engineering generate diagrams from source code and convert the revised version back into code. The fact that you don’t have to draw all instances yourself saves a lot of time and makes it even easier to document the project. However, if you draw it yourself, it makes sense to maintain a certain level of abstraction. If you then convert your diagram into code, you can at least work in neat framework.

A good tool does its job without making operation difficult with unnecessary extras. Free UML tools are sufficient for simple drafts like in use case A. To illustrate complex systems or to find solutions for program integration through diagrams (like in cases B and C), you need the best UML tools with numerous features. In the following paragraphs, we introduce you to tools with very different functional ranges.

Compared to other tools, GitMind is difficult to integrate with other processes. Only XMind data can be imported. XMind is a similar tool to GitMind with a broader focus on brainstorming. Exporting data formats is limited. Users can choose from three image formats: PNG, JPG, and SVG as well as PDF.

On the other hand, the option to collaborate is a nice feature. You can easily add other GitMind users to your team, share projects and collaborate on UML diagrams. A convenient file management system is available from which file sharing can be enabled.

All GitMind functions are available as part of the free version. Once you’ve registered on the platform, you can create, save and export UML diagrams. However, exports are limited in the free version. File sharing is available as part of the free package. With the paid subscription, you get an unlimited number of exports and customer support via email.

Before you can use Gliffy, sign in with your email address or a Google, Microsoft, or Facebook account. After the free trial period of 14 days, it can only continue to be used for free with limited functionality. However, you can upgrade to a premium account with a monthly subscription.

Gliffy has a large, well-assorted shape library. In addition to UML, you can use it to model simple flowcharts or business process modelling and notations (BPMN), among other things. At the beginning, an orientation window allows you to define your desired modelling language. If you select groups, the corresponding tools are highlighted in the menu bar. Grid and guidelines allow you to place diagram elements precisely where you want them.

The theme tool should determine the colour family for the diagram but is limited to the arrow elements in the test. By clicking on classes, components, and the like, you can still quickly adjust the colour and font of the symbols. You can also create different layers in no time by clicking on the corresponding menu item (far right in the tool bar). In addition, you do not have to plan the diagram construction step by step in advance. You can simply undo errors with the delete function. If you want to insert an element, Gliffy detects the change and suggests appropriate insert options.

As a free UML tool, Gliffy imports diagrams in GON, Gliffy, and gXML formats. For the Microsoft Visio format, VDX, you need a business account. The same applies when exporting common image formats such as JPG, PNG, and SVG and the connection to Google Drive. Free accounts also have the native ‘Gliffy’ format. Save a document in this format, share it easily with others via a download link, or embed it on various platforms such as HipChat, Slack, Confluence, or WordPress.

A free account also provides 2 MB of cloud space for your diagrams and allows you to share five models publicly at the same time. With a paid account from about £6.00 per month, Gliffy offers you even more possibilities: unlimited memory, diagram import from Visio, and export to the mentioned image formats. An enterprise account is required for significantly more performance. For such high demands, however, there is better software.

MagicDraw offers five editions (from Reader to Enterprise) that differ in both functionality and cost. In our test, we took a closer look at the Enterprise edition because it not only offers all the features and plugins for effective modelling, but also enables full integration into an integrated development environment such as Eclipse Workbench.

The UML tool imports many file formats, including native XMI metadata formats from Eclipse and IBM’s Rhapsody, CSV, ReqIF, DoDAF, and CA Erwin Data Modeler. You can save and print your diagrams as copies in the image formats BMP, PNG, JPG, and EMF. Code generation, reverse engineering and round-trip engineering are also possible. MagicDraw is based on three languages: Java, C++ in different dialects, and C#.

If you model UML diagrams yourself in an empty document or add details to modelling, you’ll quickly appreciate the customisable panels. Already at the first start of the UML diagram tool, the clear division proves to be a big plus. Add as many tabs as you consider necessary for your workflow. Despite its many functions and edition options, MagicDraw provides a clear layout and unobtrusive short explanations, so that even inexperienced users can quickly put together their first drafts without much familiarisation time.

If you select the ‘diagrams’ tab in the main menu bar, the UML tool opens the template for the selected type in the sidebar of the workspace. If you drag an element onto the worksheet and click it once, small buttons appear. Click on these (or right-click on the element) to edit the object properties, add text, or hyperlinks. The personalisation toolbar above the worksheet always highlights the tools you can use to graphically customise one or more selected items. The layout tool brings order to unstructured drafts. With the zoom and perspective panel, you have your project completely in view – from small details to the whole image.

The UML program also checks your project for errors and displays them. For independent analysis, you have the option of comparing different versions of a diagram next to each other and checking different levels of abstraction for traceability. Architects particularly appreciate the free text input for creating diagrams, as it favours a smooth workflow.

If you want to design complex diagrams with more than 60 objects, you need a premium account. The same applies if you are working on more than three active documents at the same time.

You can also import data and diagrams with the free account. The UML diagram tool supports native diagram formats from Microsoft Visio, Omnigraffle, Gliffy, and Draw.io. Drag data from CSV files, SQL, AWS architecture, and mind maps. The data linking feature also integrates real-time data from Excel, CSV, and Google Sheets. If you want to edit native formats of other providers, however, you will again need a paid account. It also allows you to back up and restore your data.

But how efficient is Lucidchart to work with? The user interface is characterised by a clear layout and plenty of space to work. The menu pops up from the right when you need it and disappears as a narrow toolbar until you need it. With one click, you can change the page settings, create layers, and presentations, or exchange information with teammates. You will find the templates in the bar to the left of the workspace. You can customise its content and size by adding templates and using the mouse to drag the width of the bar to how you want it.

The horizontal toolbar shows the tools you need each time you want to drag a shape or line onto the work area. You can easily adjust the size and orientation by clicking on the shape. If you hover over a shape with the mouse, small red circles will appear. You can add arrows and lines at these points. Use the grid and automated guides to easily draw neat diagrams. Some developers prefer to write input commands instead, building their UML diagram. The tool offers the UML mark-up function so you can do this.

The team edition allows you to customise user roles and protect your documents through single sign-on authentication. Lucidchart cloud storage also encrypts your data. Every time you share a document, you decide who can edit, comment, or just read it.

IBM Rational Rhapsody is a graphical, integrated development environment (IDE) for software and product development. The UML program supports object-based software development for web-based applications as well as embedded systems and real-time systems based on C++ and Java EE. UML/SysML modelling enables you to create source code quickly in the IDE for the specified languages, C and C#, and Ada.

Rhapsody was passed on many times after its development in 1998. After IBM acquired the Swedish company, Telelogic AB in 2008, the American company expanded its rational product range with Telelogic’s Rhapsody. The Swedes only purchased the IDE in 2006 by acquiring the original developer company, I-Logix. As one of the first graphical development environments, Rational Rhapsody, spread in a short time.

International brands use the software for large projects that require detailed version differentiation for numerous team members in different countries. Jaguar Land Rover, for example, uses Rational Rhapsody to adapt the software to its infotainment offer to different markets.

For these and other tasks, Rhapsody offers a development environment in which you can draw diagrams, generate, and check code, and compare or analyse different versions. The UML tool supports the following:

• UML
• SysML
• AUTOSAR
• DoDAF
• MODAF
• UPDM
• DSL

These UML-based modelling languages are suitable for tool-based software development, which saves programmers a lot of work. In addition, you can rely on compatibility since UML and Rhapsody were developed in the same house – namely at Rational Software.

In Rhapsody, you either draw the models freely, import existing code for visualisations as diagrams, or download requirements from a requirements management tool such as Doors, a relative of the Rational family. The following YouTube video shows you how to create a SysML model for a real-time system from a list of requirements in Doors. In this case, IBM will present its approach to the INCOSE Vendor Challenge. The aim of the project was to create a parking system for a hotel chain.

The developers built the UML tool based on the open source software Eclipse. The current version still supports the Eclipse IDE platform as an integration or a plugin. It contains further integrated development environments as workflow integration:

• Wind River Workbench
• Green Hills MULTI
• Microsoft Visual Studio 2008

As an IDE, Rhapsody works in real time and creates source code frames from diagrams. The program is available in four different license forms. In addition, IBM offers different versions of the UML tool specifically for the different requirements of different departments. The modules are compatible with the IDE. You can choose between the Architect for Systems Engineers, the Designer for Systems Engineers, the Architect for Software, or the Developer. The programs differ mainly in functionality and price.

The Developer is the full version, which combines all features and integrates your created source code into the embedded development environment. It also optimises the path from the first draft to the prototype and to the finished implementation. For example, you can use round-trip engineering and reverse engineering for this purpose. If you want to synchronise source code and design or document the process, this is also possible. Among the slim-lined versions, Architect for Software is the most powerful tool for working with UML, because it is the only one that offers these developer features.

Alternatively, you can get Visio Professional as a permanent license at a steep premium. This version includes a desktop app, the browser applications, and an iPad app. Visio Standard does not support UML diagrams and is therefore not included here. As UML tools, the Visio versions presented are primarily aimed at corporate customers who appreciate the familiar Office environment and want to optimise their workflow by seamlessly integrating the appropriate modelling tool into their existing system.

If you need a comprehensive shape library with current UML notations standards and if you have already subscribed to Microsoft Office Pro 365, we recommend Online Plan 2.

Visio is largely limited to features that allow you to draw industry-standard vector graphics and diagrams and work in a team. If you release a diagram, authorised team members can work on it simultaneously in the document as well as exchange ideas. Visio can also be integrated with Microsoft Teams to make collaboration easier. You simply share finished sketches and prototypes via the connected cloud.

If you want to create code frames from your diagrams, you need other UML tools, for example, Visual Studio from Microsoft. As this is also part of the product family, the integrated development environment allows Visio to be integrated into the development process. Save your work in the UML diagram tool in native OPC/XML metadata formats so that you can export your diagrams and continue working on them without any data loss.

Native Visio formats:

• VSD (drawing)
• VSS (stencil)
• VST (template)
• VSW (web drawing)
• VSDX (OPC/XML drawing)
• VSDM (OPC/XML drawing, macro-enabled)
• VSSX (OPC/XML stencil)
• VSSM (OPC/XML stencil, macro-enabled)
• VSTX (OPC/XML template)
• VSTM (OPC/XML template, macro-enabled)
• VSL (add-on)

Visio has neither code generation nor round-trip engineering functions. However, it enables reverse engineering where you create UML diagrams from imported data or source code. Therefore, the UML tool fulfils its main task, which consists of clearly displaying processes and systems. Visio also enables you to integrate real-time data into your diagrams with a single click. This so-called data linking illustrates complex business processes (with BPMN) during their entire runtime, for example. Alternatively, you can test dependencies within a system using a UML communication diagram – live with real data.