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Development and Contribution πŸ™Œ ​

So you want to help? That's great!

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Here are a few things to get you started on the right path.

The Docs Structure is dictated by .vitepress/config.ts.

Note: Commits and Pull Requests should be directed to the develop branch.

Branching ​

Mermaid uses a Git Flow–inspired approach to branching. So development is done in the develop branch.

Once development is done we branch a release branch from develop for testing.

Once the release happens we merge the release branch with master and kill the release branch.

This means that you should branch off your pull request from develop and direct all Pull Requests to it.

Contributing Code ​

We make all changes via Pull Requests. As we have many Pull Requests from developers new to mermaid, we have put in place a process, wherein knsv, Knut Sveidqvist is the primary reviewer of changes and merging pull requests. The process is as follows:

  • Large changes reviewed by knsv or other developer asked to review by knsv
  • Smaller, low-risk changes like dependencies, documentation, etc. can be merged by active collaborators
  • Documentation (we encourage updates to the /packages/mermaid/src/docs folder; you can submit them via direct commits)

When you commit code, create a branch with the following naming convention:

Start with the type, such as feature or bug, followed by the issue number for reference, and a text that describes the issue.

One example:


Another example:


Contributing to Documentation ​

If it is not in the documentation, it's like it never happened. Wouldn't that be sad? With all the effort that was put into the feature?

The docs are located in the src/docs folder and are written in Markdown. Just pick the right section and start typing. If you want to propose changes to the structure of the documentation, such as adding a new section or a new file you do that via .vitepress/config.ts.

All the documents displayed in the page are listed in .vitepress/config.ts.

The contents of are based on the docs from the master branch. Updates committed to the master branch are reflected in the Mermaid Docs once released.

How to Contribute to Documentation ​

We are a little less strict here, it is OK to commit directly in the develop branch if you are a collaborator.

The documentation is located in the src/docs directory and organized according to relevant subfolder.

The docs folder will be automatically generated when committing to src/docs and should not be edited manually.

We encourage contributions to the documentation at mermaid-js/mermaid/src/docs. We publish documentation using GitHub Pages with Docsify

Add Unit Tests for Parsing ​

This is important so that, if someone that does not know about this great feature suggests a change to the grammar, they get notified early on when that change breaks the parser. Another important aspect is that, without proper parsing, tests refactoring is pretty much impossible.

Add E2E Tests ​

This tests the rendering and visual appearance of the diagrams. This ensures that the rendering of that feature in the e2e will be reviewed in the release process going forward. Less chance that it breaks!

To start working with the e2e tests:

  1. Run pnpm run dev to start the dev server
  2. Start Cypress by running pnpm exec cypress open in the mermaid folder.

The rendering tests are very straightforward to create. There is a function imgSnapshotTest, which takes a diagram in text form and the mermaid options, and it renders that diagram in Cypress.

When running in CI it will take a snapshot of the rendered diagram and compare it with the snapshot from last build and flag it for review if it differs.

This is what a rendering test looks like:

it('should render forks and joins', () => {
    state fork_state <<fork>>
      [*] --> fork_state
      fork_state --> State2
      fork_state --> State3

      state join_state <<join>>
      State2 --> join_state
      State3 --> join_state
      join_state --> State4
      State4 --> [*]
    { logLevel: 0 }

Any Questions or Suggestions? ​

After logging in at, open or append to an issue using the GitHub issue tracker of the mermaid-js repository.

How to Contribute a Suggestion ​

Markdown is used to format the text, for more information about Markdown see the GitHub Markdown help page.

To edit Docs on your computer:

  1. Find the Markdown file (.md) to edit in the packages/mermaid/src/docs directory in the develop branch.
  2. Create a fork of the develop branch.
  3. Make changes or add new documentation.
  4. Commit changes to your fork and push it to GitHub.
  5. Create a Pull Request of your fork.

To edit Docs on GitHub:

  1. Login to
  2. Navigate to packages/mermaid/src/docs.
  3. To edit a file, click the pencil icon at the top-right of the file contents panel.
  4. Describe what you changed in the Propose file change section, located at the bottom of the page.
  5. Submit your changes by clicking the button Propose file change at the bottom (by automatic creation of a fork and a new branch).
  6. Create a Pull Request of your newly forked branch by clicking the green Create Pull Request button.

Last Words ​

Don't get daunted if it is hard in the beginning. We have a great community with only encouraging words. So, if you get stuck, ask for help and hints in the Slack forum. If you want to show off something good, show it off there.

Join our Slack community if you want closer contact!

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