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Mermaid
MITMarkdown-inspired diagramming library that generates Gantt charts and flowcharts from text.
Open-source alternative to — compare it against:
Overview
Mermaid
Generate diagrams from markdown-like text.
📖 Documentation | 🚀 Getting Started | 🌐 CDN | 🙌 Join Us
Try Live Editor previews of future releases: Develop | Next
:trophy: Mermaid was nominated and won the JS Open Source Awards (2019) in the category "The most exciting use of technology"!!!
Thanks to all involved, people committing pull requests, people answering questions! 🙏
Table of content
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About
Mermaid is a JavaScript-based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer to create and modify complex diagrams. The main purpose of Mermaid is to help documentation catch up with development.
Doc-Rot is a Catch-22 that Mermaid helps to solve.
Diagramming and documentation costs precious developer time and gets outdated quickly.
But not having diagrams or docs ruins productivity and hurts organizational learning.
Mermaid addresses this problem by enabling users to create easily modifiable diagrams. It can also be made part of production scripts (and other pieces of code).
Mermaid allows even non-programmers to easily create detailed diagrams through the Mermaid Live Editor.
For video tutorials, visit our Tutorials page.
Use Mermaid with your favorite applications, check out the list of Integrations and Usages of Mermaid.
You can also use Mermaid within GitHub as well many of your other favorite applications—check out the list of Integrations and Usages of Mermaid.
For a more detailed introduction to Mermaid and some of its more basic uses, look to the Beginner's Guide, Usage and Tutorials.
Our PR Visual Regression Testing is powered by Argos with their generous Open Source plan. It makes the process of reviewing PRs with visual changes a breeze.
In our release process we rely heavily on visual regression tests using applitools. Applitools is a great service which has been easy to use and integrate with our tests.
Features
- 20+ Diagram Types – Flowchart, Sequence, Class, State, ER, Gantt, Pie, Git Graph, Mindmap, Timeline, Sankey, and more
- Markdown-Inspired Syntax – Write diagrams as text, no drag-and-drop required
- No Design Tool Needed – Generate professional diagrams straight from code
- Live Editor – Prototype instantly at mermaid.live
- Version-Control Friendly – Diagrams live as text, so diffs and reviews just work
- Native GitHub Rendering – Mermaid code blocks render directly in Markdown on GitHub
- Highly Customizable – Themes, colors, fonts, and layout directions
- Security First – Built-in sanitization plus a sandboxed rendering mode
- Lightweight – Small footprint, no heavy dependencies
- Active Community – Frequent releases and thousands of contributors
- Open Source – MIT licensed
Examples
The following are some examples of the diagrams, charts and graphs that can be made using Mermaid. Click here to jump into the text syntax.
Flowchart [docs - live editor]
flowchart LR
A[Hard] -->|Text| B(Round)
B --> C{Decision}
C -->|One| D[Result 1]
C -->|Two| E[Result 2]
flowchart LR
A[Hard] -->|Text| B(Round)
B --> C{Decision}
C -->|One| D[Result 1]
C -->|Two| E[Result 2]
Sequence diagram [docs - live editor]
sequenceDiagram
Alice->>John: Hello John, how are you?
loop HealthCheck
John->>John: Fight against hypochondria
end
Note right of John: Rational thoughts!
John-->>Alice: Great!
John->>Bob: How about you?
Bob-->>John: Jolly good!
sequenceDiagram
Alice->>John: Hello John, how are you?
loop HealthCheck
John->>John: Fight against hypochondria
end
Note right of John: Rational thoughts!
John-->>Alice: Great!
John->>Bob: How about you?
Bob-->>John: Jolly good!
Gantt chart [docs - live editor]
gantt
section Section
Completed :done, des1, 2014-01-06,2014-01-08
Active :active, des2, 2014-01-07, 3d
Parallel 1 : des3, after des1, 1d
Parallel 2 : des4, after des1, 1d
Parallel 3 : des5, after des3, 1d
Parallel 4 : des6, after des4, 1d
gantt
section Section
Completed :done, des1, 2014-01-06,2014-01-08
Active :active, des2, 2014-01-07, 3d
Parallel 1 : des3, after des1, 1d
Parallel 2 : des4, after des1, 1d
Parallel 3 : des5, after des3, 1d
Parallel 4 : des6, after des4, 1d
Class diagram [docs - live editor]
classDiagram
Class01 <|-- AveryLongClass : Cool
<<Interface>> Class01
Class09 --> C2 : Where am I?
Class09 --* C3
Class09 --|> Class07
Class07 : equals()
Class07 : Object[] elementData
Class01 : size()
Class01 : int chimp
Class01 : int gorilla
class Class10 {
<<service>>
int id
size()
}
classDiagram
Class01 <|-- AveryLongClass : Cool
<<Interface>> Class01
Class09 --> C2 : Where am I?
Class09 --* C3
Class09 --|> Class07
Class07 : equals()
Class07 : Object[] elementData
Class01 : size()
Class01 : int chimp
Class01 : int gorilla
class Class10 {
<<service>>
int id
size()
}
State diagram [docs - live editor]
stateDiagram-v2
[*] --> Still
Still --> [*]
Still --> Moving
Moving --> Still
Moving --> Crash
Crash --> [*]
stateDiagram-v2
[*] --> Still
Still --> [*]
Still --> Moving
Moving --> Still
Moving --> Crash
Crash --> [*]
Pie chart [docs - live editor]
pie
"Dogs" : 386
"Cats" : 85.9
"Rats" : 15
pie
"Dogs" : 386
"Cats" : 85.9
"Rats" : 15
Git graph [experimental - live editor]
gitGraph
commit
commit
branch develop
checkout develop
commit
commit
checkout main
merge develop
commit
commit
gitGraph
commit
commit
branch develop
checkout develop
commit
commit
checkout main
merge develop
commit
commit
Bar chart (using gantt chart) [docs - live editor]
gantt
title Git Issues - days since last update
dateFormat X
axisFormat %s
section Issue19062
71 : 0, 71
section Issue19401
36 : 0, 36
section Issue193
34 : 0, 34
section Issue7441
9 : 0, 9
section Issue1300
5 : 0, 5
gantt
title Git Issues - days since last update
dateFormat X
axisFormat %s
section Issue19062
71 : 0, 71
section Issue19401
36 : 0, 36
section Issue193
34 : 0, 34
section Issue7441
9 : 0, 9
section Issue1300
5 : 0, 5
User Journey diagram [docs - live editor]
journey
title My working day
section Go to work
Make tea: 5: Me
Go upstairs: 3: Me
Do work: 1: Me, Cat
section Go home
Go downstairs: 5: Me
Sit down: 3: Me
journey
title My working day
section Go to work
Make tea: 5: Me
Go upstairs: 3: Me
Do work: 1: Me, Cat
section Go home
Go downstairs: 5: Me
Sit down: 3: Me
C4 diagram [docs]
C4Context
title System Context diagram for Internet Banking System
Person(customerA, "Banking Customer A", "A customer of the bank, with personal bank accounts.")
Person(customerB, "Banking Customer B")
Person_Ext(customerC, "Banking Customer C")
System(SystemAA, "Internet Banking System", "Allows customers to view information about their bank accounts, and make payments.")
Person(customerD, "Banking Customer D", "A customer of the bank, <br/> with personal bank accounts.")
Enterprise_Boundary(b1, "BankBoundary") {
SystemDb_Ext(SystemE, "Mainframe Banking System", "Stores all of the core banking information about customers, accounts, transactions, etc.")
System_Boundary(b2, "BankBoundary2") {
System(SystemA, "Banking System A")
System(SystemB, "Banking System B", "A system of the bank, with personal bank accounts.")
}
System_Ext(SystemC, "E-mail system", "The internal Microsoft Exchange e-mail system.")
SystemDb(SystemD, "Banking System D Database", "A system of the bank, with personal bank accounts.")
Boundary(b3, "BankBoundary3", "boundary") {
SystemQueue(SystemF, "Banking System F Queue", "A system of the bank, with personal bank accounts.")
SystemQueue_Ext(SystemG, "Banking System G Queue", "A system of the bank, with personal bank accounts.")
}
}
BiRel(customerA, SystemAA, "Uses")
BiRel(SystemAA, SystemE, "Uses")
Rel(SystemAA, SystemC, "Sends e-mails", "SMTP")
Rel(SystemC, customerA, "Sends e-mails to")
C4Context
title System Context diagram for Internet Banking System
Person(customerA, "Banking Customer A", "A customer of the bank, with personal bank accounts.")
Person(customerB, "Banking Customer B")
Person_Ext(customerC, "Banking Customer C")
System(SystemAA, "Internet Banking System", "Allows customers to view information about their bank accounts, and make payments.")
Person(customerD, "Banking Customer D", "A customer of the bank, <br/> with personal bank accounts.")
Enterprise_Boundary(b1, "BankBoundary") {
SystemDb_Ext(SystemE, "Mainframe Banking System", "Stores all of the core banking information about customers, accounts, transactions, etc.")
System_Boundary(b2, "BankBoundary2") {
System(SystemA, "Banking System A")
System(SystemB, "Banking System B", "A system of the bank, with personal bank accounts.")
}
System_Ext(SystemC, "E-mail system", "The internal Microsoft Exchange e-mail system.")
SystemDb(SystemD, "Banking System D Database", "A system of the bank, with personal bank accounts.")
Boundary(b3, "BankBoundary3", "boundary") {
SystemQueue(SystemF, "Banking System F Queue", "A system of the bank, with personal bank accounts.")
SystemQueue_Ext(SystemG, "Banking System G Queue", "A system of the bank, with personal bank accounts.")
}
}
BiRel(customerA, SystemAA, "Uses")
BiRel(SystemAA, SystemE, "Uses")
Rel(SystemAA, SystemC, "Sends e-mails", "SMTP")
Rel(SystemC, customerA, "Sends e-mails to")
Release
For those who have the permission to do so:
Update version number in package.json.
npm publish
The above command generates files into the dist folder and publishes them to https://www.npmjs.com.
Related projects
Contributors 
Mermaid is a growing community and is always accepting new contributors. There's a lot of different ways to help out and we're always looking for extra hands! Look at this issue if you want to know where to start helping out.
Detailed information about how to contribute can be found in the contribution guide
Security and safe diagrams
For public sites, it can be precarious to retrieve text from users on the internet, storing that content for presentation in a browser at a later stage. The reason is that the user content can contain embedded malicious scripts that will run when the data is presented. For Mermaid this is a risk, specially as mermaid diagrams contain many characters that are used in html which makes the standard sanitation unusable as it also breaks the diagrams. We still make an effort to sanitize the incoming code and keep refining the process but it is hard to guarantee that there are no loop holes.
As an extra level of security for sites with external users we are happy to introduce a new security level in which the diagram is rendered in a sandboxed iframe preventing javascript in the code from being executed. This is a great step forward for better security.
Unfortunately you cannot have a cake and eat it at the same time which in this case means that some of the interactive functionality gets blocked along with the possible malicious code.
Reporting vulnerabilities
To report a vulnerability, please e-mail [email protected] with a description of the issue, the steps you took to create the issue, affected versions, and if known, mitigations for the issue.
Appreciation
A quick note from Knut Sveidqvist:
Many thanks to the d3 and dagre-d3 projects for providing the graphical layout and drawing libraries!
Thanks also to the js-sequence-diagram project for usage of the grammar for the sequence diagrams. Thanks to Jessica Peter for inspiration and starting point for gantt rendering.
Thank you to Tyler Long who has been a collaborator since April 2017.
Thank you to the ever-growing list of contributors that brought the project this far!
Mermaid was created by Knut Sveidqvist for easier documentation.
