A Gantt chart is a horizontal bar chart that visualizes a project schedule over time, showing tasks, their durations, dependencies, and milestones against a calendar — a staple of project planning that increasingly appears as code-generated diagrams in API and software documentation.
Gantt Charts
Gantt charts are horizontal bar charts that lay a project’s tasks out against a timeline, so you can see at a glance what happens when, how long each piece takes, and which tasks depend on others. Named after Henry Gantt, who popularized them in the 1910s, they have become the default visual language for project scheduling across nearly every industry. Each bar represents a task, its position and length encode start date and duration, and connectors express dependencies.
- Tasks over time - Each bar is a task plotted against a calendar axis, making duration and sequence immediately readable.
- Dependencies - Links between bars express that one task must finish (or start) before another can begin.
- Milestones - Zero-duration markers flag key deadlines, releases, or decision points.
- Progress tracking - Bars can be shaded or annotated to show percent-complete against plan.
For API and software teams, Gantt charts increasingly live as code rather than as artifacts locked inside a proprietary tool. Diagram-as-code tools like Mermaid let you author a Gantt chart in plain text inside a Markdown file, so a release schedule or a deprecation timeline can sit right in the repository next to the OpenAPI definition it describes and stay under version control. That makes them a natural fit for API roadmaps, migration plans, and the kind of governance documentation that needs to be both human-readable and diff-able over time.
