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Timeline

Back to Style Guide — Read the style guide first for emoji, color, and accessibility rules.

Syntax keyword: timeline Best for: Chronological events, historical progression, milestones over time, release history When NOT to use: Task durations/dependencies (use Gantt), detailed project plans (use Gantt)

⚠️ Accessibility: Mermaid 12.0.0 accepts accTitle/accDescr, but the tested timeline SVG omitted their metadata. Supply a visible description and export alt text.

Exemplar Diagram

Timeline of a startup's growth milestones from founding through Series A, organized by year and quarter:

timeline
    title 🚀 Startup Growth Milestones
    section 2024
        Q1 : 💡 Founded : Built MVP
        Q2 : 🧪 Beta launch : 100 users
        Q3 : 📈 Product-market fit : 1K users
        Q4 : 💰 Seed round : $2M raised
    section 2025
        Q1 : 👥 Team of 10 : Hired engineering lead
        Q2 : 🌐 Public launch : 10K users
        Q3 : 🏢 Enterprise tier : First B2B deal
        Q4 : 📊 $1M ARR : Series A prep
    section 2026
        Q1 : 🚀 Series A : $15M raised

Tips

• Use section to group by year, quarter, or phase
• Each entry can have multiple items separated by :
• Time labels are categorical strings in source order; horizontal spacing does not encode elapsed duration
• Keep items concise — 2–4 words each
• Emoji at the start of key items for visual anchoring
• Always pair with a Markdown text description above for screen readers

Template

Description of the timeline and the period it covers:

timeline
    title 📋 Your Timeline Title
    section Period 1
        Event A : Detail one : Detail two
        Event B : Detail three
    section Period 2
        Event C : Detail four
        Event D : Detail five : Detail six

Complex Example

Multi-year technology platform evolution tracking a startup's journey from monolith through microservices to AI-powered platform. Six sections span 2020-2025, each capturing key technical milestones and business metrics that drove architecture decisions:

timeline
    title 🚀 Platform Architecture Evolution
    section 2020 — Monolith Era
        Q1 : 💡 Founded company : Rails monolith launched : 10 engineers
        Q3 : ⚠️ Hit scaling ceiling : 50K concurrent users : Database bottleneck
    section 2021 — Breaking Apart
        Q1 : 🔐 Extracted auth service : 🐳 Adopted Docker : CI/CD pipeline live
        Q3 : 📦 Split order processing : ⚡ Added Redis cache : 200K users
    section 2022 — Microservices
        Q1 : ⚙️ 8 services in production : ☸️ Kubernetes migration : Service mesh pilot
        Q3 : 📥 Event-driven architecture : 📊 Observability stack : 500K users
    section 2023 — Platform Maturity
        Q1 : 🌐 Multi-region deployment : 🛡️ Zero-trust networking : 50 engineers
        Q3 : 🔄 Canary deployments : 📈 99.99% uptime SLA : 2M users
    section 2024 — AI Integration
        Q1 : 🧠 ML recommendation engine : ⚡ Real-time personalization
        Q3 : 🔍 AI-powered search : 📊 Predictive analytics : 5M users
    section 2025 — Next Generation
        Q1 : ☁️ Edge computing rollout : 🤖 AI agent platform : 10M users

Why this works

• 6 sections are eras, not just years — "Monolith Era", "Breaking Apart", "Microservices" tell the story of why the architecture changed, not just when
• Business metrics alongside tech milestones — user counts and team size appear next to architecture decisions. This shows the pressure that drove each evolution (50K users → scaling ceiling → extracted services)
• Multiple items per time point — each quarter packs 2-3 items separated by :, giving a dense but scannable view of everything happening in parallel
• Emoji anchors the scan — eyes land on 🧠 ML, 🌐 Multi-region, ⚡ Redis before reading the text. For a quick skim, the emoji alone tells the story

Verified reference

Syntax examples reviewed against official Mermaid documentation and rendered with Mermaid 12.0.0 (2026-10-01). Check the destination version; appearance and accessibility are not guaranteed by a successful parse.