How do I add multiple events to the same time period in a Mermaid timeline?

Place additional events on indented lines immediately below the time label, each starting with `:`. Example: `2023 : ChatGPT releases GPT-4 \n : Anthropic launches Claude 2 \n : Google releases Gemini`. Each `: event` line renders as a separate event box stacked under the `2023` time marker. This is useful for years with multiple significant milestones.

How do I group timeline events into sections?

Use `section SectionName` before a group of time periods. Sections visually separate the timeline into labeled phases — for example `section Development Phase` followed by year entries, then `section Launch Phase` for the next group. Sections render as colored background bands that help readers navigate long timelines with distinct phases.

What is the difference between a Mermaid timeline and a Gantt chart?

A Mermaid timeline is optimized for showing when events occurred — it accepts text labels and dates without precise duration or dependency information. A Gantt chart is better for planning — it shows tasks with exact start dates, durations, and dependencies. Use a timeline for retrospectives, history, and roadmap overviews; use a Gantt chart for sprint planning, resource allocation, and scheduling.

Is the Mermaid timeline diagram type available in GitHub and GitLab?

GitHub added native Mermaid rendering in 2022, and GitLab has supported it since 2019. However, the `timeline` diagram type requires Mermaid v9.4 or later. If you see a parsing error for a timeline on GitHub or GitLab, the platform may be using an older bundled version of Mermaid. Zolkit always uses the latest Mermaid version, so timeline diagrams are fully supported here regardless of platform compatibility.

Mermaid Timeline Diagram Viewer

Render Mermaid timeline diagrams in your browser. Visualize historical events, product roadmaps, and milestones. Export SVG or PNG.

Mermaid Code

Preview

Enter Mermaid code to preview your diagram

Timeline diagrams visualize events in chronological order, making them ideal for product roadmaps, historical narratives, technology evolution stories, and project retrospectives. Mermaid's `timeline` diagram type — introduced in v9.4 — offers a clean, readable format for marking what happened when without the complexity of a full Gantt chart. AI assistants use Mermaid timelines when asked to summarize historical developments ('Show the history of JavaScript frameworks'), present product evolution ('Map our product milestones from 2020 to today'), or outline a release roadmap ('Create a timeline for our Q1–Q4 2025 product plan'). Pasting the generated code into Zolkit renders the timeline immediately so you can check that the events are accurate, well-labeled, and appropriately spaced before including it in a presentation or document. Zolkit's timeline viewer supports multiple events per time period (shown as stacked boxes under the same time label), section grouping for organizing phases, and the full range of Mermaid timeline styling. The exported SVG or PNG is suitable for pitch decks, company history pages, engineering all-hands slides, and annual review documents.

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Free Online Mermaid Diagram Viewer and Exporter

Zolkit's Mermaid Diagram Viewer lets you paste any Mermaid code and see a rendered diagram instantly — no installation, no sign-up, no server uploads. Everything runs in your browser, making it the fastest way to verify AI-generated diagrams from Claude, ChatGPT, or Gemini. Supports all major Mermaid diagram types: flowcharts, sequence diagrams, class diagrams, ER diagrams, Gantt charts, state diagrams, mind maps, Git graphs, pie charts, and timelines.

Instant Live Preview

Diagrams render automatically as you type, with a 300ms debounce so it never feels sluggish.

100% Private

All rendering happens in your browser using mermaid.js. Your code is never sent to any server.

Export SVG & PNG

Download your diagram as a crisp vector SVG or a high-resolution 2× PNG ready for docs and slides.

All Mermaid Diagram Types

Supports flowcharts, sequence diagrams, class diagrams, ER diagrams, Gantt charts, mind maps, Git graphs, and more.

AI Diagram Ready

Built for the AI era — directly preview diagrams generated by Claude, ChatGPT, Gemini, or any LLM.

Always Free

No account needed, no usage limits, no watermarks. Zolkit's Mermaid viewer is completely free forever.

How to Preview a Mermaid Diagram

1
Paste your Mermaid code into the editor on the left — you can copy it from an AI assistant or write it manually.
2
The diagram renders instantly in the preview panel on the right. If there's a syntax error, a message explains the issue.
3
Click 'Export SVG' or 'Export PNG' to download your diagram as a file ready for documentation, slides, or sharing.