Gantt Chart

gantt Product Launch 2024
start 2026-03-15
today-marker
critical-path
dependencies

holiday
  2024-02-19 Presidents Day
  2024-05-27 Memorial Day

tag Team alias t
  Engineering(blue)
  Design(purple)
  QA(orange)
  Marketing(green)

tag Phase alias p
  Foundation(teal)
  Build(blue)
  Launch(red)

era 2026-04-06 -> 2026-04-10 RSA Conference (purple)
marker 2026-03-27 Board Review
marker 2026-05-12 Trade Show Demo (orange)

parallel
  [Backend] | t: Engineering
    20bd Database Schema | p: Foundation, 100%
    15bd? Core API Endpoints | p: Foundation, 80%
      -> Frontend.API Integration
    10bd Auth & Permissions | p: Build, 40%
      -> E2E Testing
    parallel
      5bd Load Testing | t: QA, p: Build
      5bd Security Audit | t: QA, p: Build

  [Frontend] | t: Design
    10bd Wireframes & Prototypes | p: Foundation, 100%
    15bd Component Library | p: Build, 60%
    10bd API Integration | t: Engineering, p: Build
      // Blocked until Core API is stable
    5bd Polish & Animations | p: Launch, 10%

  [Marketing] | t: Marketing
    10bd? Brand Guidelines | p: Foundation, 100%
    15bd Landing Page | p: Build, 50%
    5bd? Launch Campaign Prep | p: Launch
      -> Launch Day

[Integration] | t: QA
  10bd E2E Testing | p: Launch, offset: 10bd
  3bd Staging Deploy | p: Launch
  0d Launch Day

Overview

Gantt charts visualize project schedules as horizontal bars on a time axis. Tasks have durations, can be grouped, run in parallel, and linked with dependencies. The renderer automatically calculates dates from durations and shows critical path highlighting.

Syntax

gantt Project Name
start 2024-01-15

[Group Name]
  30d Task label
  10bd Another task | tag: Value

Settings

Key	Description	Default
`chart`	Must be `gantt`	—
`title`	Chart title	None
`start`	Project start date (`YYYY-MM-DD`)	Today
`today-marker`	Show today marker (bare keyword or a `YYYY-MM-DD` date)	off
`critical-path`	Highlight the critical path	off
`dependencies`	Show dependency arrows	off
`sort`	Task sorting: `default` or `tag` (swimlane by tag)	`default`

Tasks

Tasks are defined with a duration followed by a space and label:

30d Database Layer
10bd Auth Module
5w Long Research Phase

Duration Units

Unit	Meaning
`d`	Calendar days
`bd`	Business days
`w`	Weeks
`m`	Months
`q`	Quarters
`y`	Years

Explicit Start Dates

Pin a task to a specific start date:

2024-03-01 -> 15bd Task starting March 1st

Milestones

Use 0d for zero-duration milestones:

0d Release Candidate

Uncertain Duration

Add ? after the unit to indicate an uncertain end date. The bar fades out over the last 20%:

30bd? Estimated research phase

Progress

Add a percentage to show task completion:

30bd Database Layer | 80%
10bd Auth Module | 100%

Groups

Groups organize tasks into labeled sections using bracket syntax:

[Backend]
  30bd Database Layer
  10bd Auth Module

[Frontend]
  15bd Component Library
  10bd API Integration

Groups can be nested:

[Backend]
  [API]
    10bd REST endpoints
    5bd GraphQL layer
  [Data]
    15bd Schema design

Group Colors

Add a color suffix or use pipe metadata:

[Backend](blue)
[Frontend] | t: Engineering

Parallel Blocks

Use parallel to run groups or tasks concurrently instead of sequentially:

parallel
  [Backend]
    30bd Database Layer
    10bd Auth Module

  [Frontend]
    15bd Component Library
    10bd API Integration

Tasks inside a parallel block start at the same time. Without parallel, groups run sequentially.

Dependencies

Use -> TargetName indented under a task to create a dependency. The target task won't start until the source finishes:

[Backend]
  10bd Auth Module
    -> Frontend.API Integration

[Frontend]
  15bd Component Library
  10bd API Integration

Cross-group references use dot notation: GroupName.TaskName.

Dependencies require dependencies in the chart options to render arrows.

Dependency Offset

Add an offset to delay (or advance) the start of a dependent task relative to its predecessor. Use | offset: on a dependency line:

[Backend]
  10bd Auth Module
    -> Frontend.API Integration | offset: 3bd

[Frontend]
  15bd Component Library
  10bd API Integration

Here, "API Integration" starts 3 business days after "Auth Module" finishes, instead of immediately.

Use a negative value for lead time (overlap with predecessor):

5bd Design Review
  -> Implementation | offset: -2d

Offset accepts any duration unit (d, bd, w, m, q, y).

Task-Level Offset

Tasks can also have an offset: to shift their start date relative to where they'd normally begin (after the preceding task in their group):

[Backend]
  10bd API Layer
  5bd Auth Module | offset: 3bd

Here, "Auth Module" starts 3 business days after "API Layer" finishes instead of immediately.

Holidays

Define non-working days inside a holidays block:

holiday
  2024-12-25 Christmas
  2024-12-31 -> 2025-01-01 New Year

Business day durations (bd) automatically skip holidays and non-workdays.

Custom Workweek

Override the default Mon–Fri workweek:

workweek sun-thu

Eras

Background shaded regions spanning a time range:

era 2024-01 -> 2024-06 Phase 1
era 2024-07 -> 2024-12 Phase 2 (green)

Markers

Vertical date markers for key milestones:

marker 2024-03-01 Kickoff
marker 2024-06-30 Demo Day (red)

Tag Groups

Tag groups categorize tasks with color-coded values:

tag Team alias t
  Engineering(blue)
  Design(purple)
  QA(orange)

tag Phase alias p
  Foundation(green)
  Growth(orange)

[Backend] | t: Engineering
  30bd Database Layer | p: Foundation
  10bd Auth Module | p: Foundation

Swimlane Mode

Use sort: tag (or sort: tag:GroupName) to organize tasks into horizontal swimlanes grouped by tag value. Each tag value gets its own collapsible lane:

sort tag:Team

tag Team alias t
  Frontend(blue)
  Backend(green)
  QA(orange)

[Sprint 1]
  10bd API endpoints | t: Backend
  15bd UI components | t: Frontend
  5bd Integration tests | t: QA

In the app, click the swimlane icon on a tag pill to switch between swimlane groups.

Comments

Lines starting with // are comments and are ignored:

[Backend]
  30bd Database Layer
  // This depends on schema finalization
  10bd Auth Module

Complete Example

gantt Product Launch Plan
start 2024-01-15
today-marker 2024-03-01
critical-path
dependencies

tag Team alias t
  Engineering(blue)
  Design(purple)
  QA(orange)

era 2024-01 -> 2024-06 Phase 1
marker 2024-03-01 Kickoff

parallel
  [Backend] | t: Engineering
    30bd Database Layer | 80%
    10bd? Auth Module | 100%
      -> Frontend.API Integration | offset: 2bd
    parallel
      5bd Load Testing | t: QA
      5bd Security Audit | t: QA

  [Frontend] | t: Design
    15bd Component Library
    10bd API Integration | t: Engineering
    5bd Polish | 30%

[Integration] | t: QA
  10bd E2E Testing
  0d Release Candidate