What Is Mermaid.js?

Mermaid.js is a JavaScript library that allows users to create different types of diagrams, using a simple syntax. It supports a variety of diagram types, including flowcharts, sequence diagrams, Gantt charts, and class diagrams.

Mermaid diagrams can be easily embedded in websites, blogs, and documentation, making them a popular choice for technical writers, software developers, and other professionals who need to visualize complex information. Mermaid is open-source and can be used for both personal and commercial projects, making it a versatile tool for a variety of applications.

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Mermaid.js: Benefits and Limitations

Mermaid.js provides numerous benefits for those who need to create and share diagrams and flowcharts. Here are some of the key advantages of using Mermaid.

  • Text-based: Mermaid diagrams are created using a text string, which makes it easy to maintain compared to graphical images.
  • Integrates into products and websites: Mermaid can be easily integrated into products and websites using a simple script tag. This makes it easy to incorporate diagrams into web-based applications and other digital products.
  • Integrates into documentation tools: These include custom documentation tools such as Gatsby and Docsify, which make it easy to include diagrams and flowcharts in technical documentation.
  • Easy to use: Mermaid provides users with a simple syntax that is easy to learn and use. The Mermaid Live Editor and CLI tools make it even easier to create and edit diagrams.
  • Integrates with editor plugins: Mermaid can be integrated with editor plugins such as Visual Studio Code and Sublime Text, making it easier to update documentation and keep diagrams up-to-date.

Although Mermaid.js is a popular JavaScript library for building diagrams, it has several limitations that users should be aware of. Here are some of the limitations of Mermaid.js:

  • Limited editing experience: Mermaid’s live editor renders Mermaid’s code, but there is no graphical interface that allows the user to easily add nodes or drag them around, for example.
  • Outdated diagrams: As with many other tools, diagrams are not automatically kept up-to-date as the reality they describe evolves. This is especially important for diagrams describing code, which tends to change on a frequent basis.
  • Limited interactivity: Mermaid.js does not offer a high level of interactivity, which means that users cannot interact with the diagrams and flowcharts in the same way that they can with other libraries. For example, it is not possible to add tooltips or other interactive elements to the diagrams.
  • Limited animation support: Mermaid.js does not offer extensive support for animations, which may limit its usefulness in certain contexts. While basic animations such as fading in and out are supported, more complex animations may not be possible.
  • Limited styling options: While Mermaid.js does allow for some customization of the appearance of the diagrams and flowcharts, it has limited styling options compared to other diagramming libraries. This can make it more difficult to create diagrams that match the design and branding of a particular website or application.
  • Limited browser support: Mermaid.js may not be fully supported by all web browsers, which could limit its usefulness for some users. This can also make it more difficult to ensure that diagrams and flowcharts display correctly across different platforms and devices.

Mermaid js with Swimm

With Swimm’s Mermaid integration, you can create diagrams and charts that automatically remain up to date as code changes. Swimm allows you to include in your diagrams paths or tokens from your code, like variable names, function names, values or anything else. Swimm will track these tokens as your code evolves and update the diagrams for you. This means that diagrams in your documentation stay up to date with your code 🤯

Learn more about creating up-to-date diagrams with Mermaid js and Swimm

Top Mermaid.js Alternatives


PlantUML is a text-based diagram generation tool that allows users to generate various types of diagrams using a simple syntax. It is open-source, and supports a wide range of diagram types, including sequence diagrams, flowcharts, activity diagrams, and class diagrams.

Similar to Mermaid.js, the text-based approach of PlantUML allows users to build diagrams using plain text instead of visual editing tools. This makes it easier to version control diagrams, collaborate with others, and integrate with other text-based tools such as documentation generators.

PlantUML also features smart layout algorithms that help to automatically organize and align diagram elements. This saves time and effort in diagram creation and ensures that the resulting diagrams are professional-looking and easy to understand.

Another advantage of PlantUML is its customizability. Users can adjust the appearance of their diagrams using various configuration options, including font size, color, and shape. This allows users to generate diagrams that fit the specific needs of their projects and match their branding and visual style.


Graphviz is a popular open-source graph visualization tool that helps users visualize data and information through automated diagrams and graphs. It provides a simple way to create graphs and networks programmatically, allowing users to generate diagrams in a range of formats, including PDF, SVG, and PNG.

Graphviz uses a plain text input file to define graphs and their properties, allowing users to specify nodes, edges, labels, and styles. This makes it easy for users to generate complex graphs and networks quickly and efficiently. Graphviz is widely used in scientific research, engineering, and other technical fields, where visualizing large amounts of data is essential for understanding and analyzing complex systems.


Kroki is an open-source project that provides a unified API for generating diagrams and charts using simple text-based commands. It is designed to simplify the process of creating diagrams and charts by allowing users to focus on the content rather than the layout and styling.

Kroki supports a wide range of diagram and chart types, including UML diagrams, sequence diagrams, flowcharts, and Gantt charts. The diagrams and charts are generated dynamically on the server-side and returned as SVG, PNG, or PDF images.

Kroki provides a simple RESTful API for generating diagrams and charts using text-based commands. You can send a request to the Kroki API with a diagram definition in the request body, and Kroki will generate the diagram and return it as an image.


D2, also known as D2lang, is a diagramming language that supports a wide range of diagrams, including class diagrams, sequence diagrams, flowcharts, and more. It is designed with an engineer’s focus, providing tools that make it easy to build professional diagrams or flowcharts quickly and efficiently.

One unique feature of D2 is its ability to create custom elements and shapes. This means that users can create custom symbols and shapes to use in their diagrams, allowing for greater customization and flexibility.

D2 is also supported by Terrastruct, a cloud-based diagramming tool that allows users to create and share diagrams online. Terrastruct provides a user-friendly interface for working with D2 diagrams, making it easy for users to create and share diagrams with their team members and collaborators.


Draw.io, also known as Diagrams.net, is a free online diagramming tool that enables users to create a wide range of diagrams, including network diagrams, mind maps, and more. The interface is user-friendly, providing a variety of tools and customization options for creating professional-looking diagrams quickly and efficiently.

Draw.io is available both online and offline, as a cross-browser web application or desktop app. This makes it easy to use on various platforms, including Windows, macOS, and Linux. Draw.io also offers integration with popular cloud storage services, such as Dropbox, Google Drive, GitHub, and OneDrive, allowing users to save and access their diagrams easily from anywhere.


In conclusion, while Mermaid.js is a powerful and versatile tool for creating diagrams and flowcharts, there are several alternatives available that may better suit the needs of different users. Each of the alternatives discussed in this article offers unique features and benefits, such as compatibility with specific programming languages, greater customizability, or more intuitive interfaces.

With Swimm, Mermaid diagrams can be automatically updated as the code they describe changes.

It’s important to consider the specific requirements of your project or workflow when choosing a diagramming tool, as different tools may excel in different areas. Ultimately, the key is to find a tool that meets your needs and allows you to create professional diagrams and flowcharts quickly and efficiently. Whether you choose an open-source tool like Graphviz, a text-based tool like PlantUML, or a cloud-based tool like Draw.io, the right diagramming tool can help streamline your work and communicate complex information visually.

Read our guide to Mermaid js alternative

See Additional Guides on Key Software Development Topics

Together with our content partners, we have authored in-depth guides on several other topics that can also be useful as you explore the world of software development.

Technical Documentation

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Code Documentation

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