State Diagram
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Mermaid Studio provides full language support for State diagrams inside IntelliJ-based IDEs. State diagrams visualize the states an entity can be in and the transitions between those states, and are invaluable for modeling workflows, user interfaces, protocol behavior, and any system with distinct operational modes.
Syntax Highlighting
Section titled “Syntax Highlighting”Syntax highlighting integrates directly with IntelliJ’s color scheme system, so diagram colors always match your editor theme.
IDE Support
Section titled “IDE Support”The summary below shows the IDE support Mermaid Studio ships for state diagrams, grouped by capability.
Folding lets you collapse and expand structural blocks of the diagram source (subgraphs, frontmatter, multi-line strings) directly in the editor gutter. It keeps long diagrams navigable without forcing you to scroll past detail you don’t need right now.
Use the gutter triangles, Code → Folding, or the standard JetBrains shortcuts (
When the cursor sits next to a bracket, brace, or paren, Mermaid Studio highlights its matching pair across the whole diagram and lets you jump between them. This is especially valuable in nested syntax (subgraph blocks, JSON-style style strings, multi-shape labels) where it’s easy to lose track of which closer goes with which opener.
The line-comment action (
When you type a quote character to start a string, Mermaid Studio inserts the matching closing quote and places the cursor between them. Backspacing through an empty pair removes both characters at once. This keeps quoted labels balanced and reduces fiddly cursor work.
The formatter rewrites your diagram source to a canonical layout (consistent indentation, alignment of multi-line links, normalized whitespace around operators) without changing semantics.
It also clears up the whitespace mistakes that Mermaid’s parser is picky about, normalizing spacing between tokens so the parser accepts the diagram on the first read instead of throwing a confusing syntax error.
Run it with Code → Reformat Code (
Pressing
Live templates expand a short abbreviation into a larger snippet, with tab stops for the parts you fill in.
Type the abbreviation, press
A dedicated Grammar-Kit parser backs the highlighting, so tokens are colored by what they mean in the diagram (a type reference versus a label versus a style), not just what they look like. The same parser validates the syntax as you type, flagging malformed statements in place instead of letting one mistake cascade through the file.
This is the foundation richer features build on; the same grammar drives completions, refactoring, and inspections.
Per-diagram annotators apply rule-based highlighting above the lexer and parser, running on every keystroke and painting their results directly in the editor. Mermaid Studio uses them across the full range the platform supports: highlighting that token types alone cannot decide (coloring a reference by what it resolves to), semantic errors and warnings (an edge pointing at an undefined node, an invalid direction value), and inline cues such as marking duplicate labels. Unlike inspections (configurable checks listed in Settings), annotators are always on, whether a rule ends in a color or a warning.
As you type, Mermaid Studio offers context-aware suggestions filtered to what’s valid at the cursor: node shapes, arrow types, keywords, icon names, identifiers, frontmatter keys, theme variables, and more. Completions cut down on typos and make the diagram syntax self-documenting.
Completion and validation for the YAML frontmatter block above the diagram body, driven by the diagram type’s slice of the Mermaid config schema. Config keys, enum values, and color properties complete as you type, and unknown or mistyped keys are flagged in place.
Hex, named, and rgb()/hsl() colors in style declarations get a small color swatch rendered in the gutter.
Click the swatch to open the IntelliJ color picker and pick a new value, and the source updates in place.
A dedicated page under Settings → Editor → Color Scheme for the diagram type, listing every highlighting attribute its parser produces with a live preview. This is what makes the difference between “the theme colors it somehow” and “you decide exactly how keywords, identifiers, labels, and styles render”.
Inspections are static analyzers that run continuously and surface problems as you edit: duplicate IDs, undefined references, malformed syntax, deprecated patterns, missing required fields. Each inspection has a configurable severity (error, warning, info), can be suppressed inline, and most ship with a quick fix that resolves the issue with one keystroke.
This is where most of the editorial intelligence lives: a diagram type with rich inspections is much harder to break in subtle ways.
Rename refactoring (
Find Usages (
Code Vision renders small inline indicators above declarations, typically reference counts (“5 references”, “3 inbound edges”), so you can see at a glance how connected an element is without running Find Usages. Click an indicator to jump to the references list.
Remove the selected elements and their source, including batch deletion of a multi-selection.
Rename updates state names everywhere they appear, including comma-separated class A,B,C styleName targets.
Parse errors inside a composite state stay contained in that body, so sibling states and transitions keep their highlighting and validation.
Live templates
Section titled “Live templates”A set of 13 context-aware live templates scaffolds state declarations, transitions, and notes. Type a short abbreviation, accept it from the completion popup, and tab through the template variables.
Individual abbreviations can be toggled under Settings > Tools > Mermaid Studio > Live Templates in the State Diagram group. See Live Templates for the cross-cutting mechanics (triggering, contextual visibility, configuration).
State declarations
Section titled “State declarations”| Abbreviation | Expansion |
|---|---|
sa | Aliased state with description (state "..." as Name) |
sc | Composite state with body |
sch | Choice pseudo-state (state Name <<choice>>) |
sf | Fork pseudo-state (state Name <<fork>>) |
sj | Join pseudo-state (state Name <<join>>) |
Transitions
Section titled “Transitions”| Abbreviation | Expansion |
|---|---|
tr | Transition (From --> To) |
trl | Transition with label (From --> To : event) |
trs | Transition from start ([*] --> To) |
tre | Transition to end (From --> [*]) |
| Abbreviation | Expansion |
|---|---|
nl | Note left of state (inline form) |
nr | Note right of state (inline form) |
nlm | Note left of state (multi-line form) |
nrm | Note right of state (multi-line form) |
Quick Syntax Reference
Section titled “Quick Syntax Reference”stateDiagram-v2 [*] --> Active
state Active { [*] --> Working Working --> Waiting : pause Waiting --> Working : resume }
Active --> Inactive : disable Inactive --> Active : enable Inactive --> [*]
note right of Active : Main operational stateKey elements:
[*]- Initial and final statesstate1 --> state2- Transition between statesstate1 --> state2 : event- Transition with event labelstate Name { }- Composite (nested) statenote- Add notes to states
For complete syntax details, see the Mermaid State Diagram documentation.