How to View Mermaid Diagrams on Android — Free Apps Compared

Mermaid diagrams are everywhere in modern documentation — README.md files, architecture docs, project wikis, and technical specifications. But viewing them on Android is a challenge because most Markdown apps simply show the raw code instead of rendering the actual diagram.

If you see something like this on your phone instead of a flowchart:

```mermaid
graph TD
    A[Start] --> B{Decision}
    B -->|Yes| C[Action 1]
    B -->|No| D[Action 2]
```

…then your app doesn’t support Mermaid rendering. Here’s how to fix that.

Which Apps Actually Render Mermaid Diagrams?

Out of the dozens of Markdown apps available for Android, only three render Mermaid diagrams natively:

Every other Markdown app — Markor, MD Reader, PilcrowMD, Simple Markdown, Markdot — does not render Mermaid diagrams.

1. MerMD — Best Free Mermaid Viewer for Android ⭐

MerMD is purpose-built for viewing Markdown files with Mermaid diagrams. It renders all Mermaid diagram types natively on-device:

Supported Diagram Types

• Flowcharts (graph TD, graph LR) — process flows, decision trees, system architecture
• Sequence diagrams — API interactions, message flows, protocol exchanges
• Gantt charts — project timelines, sprint planning, milestone tracking
• Class diagrams — object-oriented design, inheritance hierarchies
• ER diagrams — database schema, entity relationships
• Pie charts — data distribution, survey results
• State diagrams — state machines, workflow states
• User journey maps — user experience flows

Why MerMD is Best for Mermaid

1. All rendering happens offline — no server calls, no API, no latency. Open a file and diagrams render instantly.
2. Diagrams adapt to themes — switch between dark and light mode, and diagrams adjust their colors automatically.
3. Cloud integration — open Mermaid-containing docs directly from GitHub, GitLab, OneDrive, or Dropbox without downloading them first.
4. Export diagrams — save rendered documents (including diagrams) as PDF, HTML, or high-resolution images.
5. Lightweight — only ~6 MB. No vault setup, no plugins, no configuration.

Download: mermd.tech

2. Obsidian — Best for Vault-Based Docs

Obsidian supports Mermaid diagrams as a core feature. If your Mermaid-containing documents are part of a larger Obsidian vault, this is the natural choice.

Pros:

• Mermaid rendering in Live Preview mode
• Bi-directional linking for connected documentation
• Desktop-to-mobile sync

Cons:

• ~80 MB app size
• Requires vault setup before viewing anything
• No direct GitHub/GitLab integration
• Sync costs $8/month

Best for: Users who already use Obsidian on desktop.

3. Markdown Viewer Editor by OpenIoTHub — Split-View Alternative

This app offers WYSIWYG editing with Mermaid support in a split-view layout.

Pros:

• Split-view with source and preview
• Supports most Mermaid diagram types

Cons:

• Less reliable offline rendering
• Slower diagram generation
• Less polished UI

Common Mermaid Diagram Examples

Here are the most common Mermaid diagrams you’ll encounter in documentation:

Flowchart (Most Common)

graph TD
    A[User Request] --> B{Authenticated?}
    B -->|Yes| C[Process Request]
    B -->|No| D[Redirect to Login]
    C --> E[Return Response]
    D --> F[Show Login Form]

Sequence Diagram

sequenceDiagram
    Client->>API Gateway: HTTP Request
    API Gateway->>Auth Service: Validate Token
    Auth Service-->>API Gateway: Token Valid
    API Gateway->>Backend: Forward Request
    Backend-->>API Gateway: Response
    API Gateway-->>Client: HTTP Response

Gantt Chart

gantt
    title Project Timeline
    dateFormat YYYY-MM-DD
    section Phase 1
    Research      :a1, 2026-01-01, 14d
    Design        :a2, after a1, 7d
    section Phase 2
    Development   :b1, after a2, 30d
    Testing       :b2, after b1, 14d

All three of these render perfectly in MerMD — try opening a .md file containing these blocks on your phone.

FAQ

Can I view Mermaid diagrams without internet?

Yes — MerMD and Obsidian both render Mermaid diagrams completely offline. All processing happens on-device.

Which app renders diagrams the fastest?

MerMD has the fastest Mermaid rendering of any Android app we’ve tested. Diagrams appear almost instantly, even for complex flowcharts.

Can I export Mermaid diagrams as images?

MerMD can export entire rendered documents (including diagrams) as high-resolution PNG images. This is great for sharing architecture diagrams in presentations.

Do these apps support the latest Mermaid syntax?

MerMD and Obsidian both use recent versions of the Mermaid.js library and support the latest syntax features.

The Bottom Line

If you need to view Mermaid diagrams on Android, MerMD is the best free option. It’s lightweight (6 MB), renders all diagram types offline, integrates with cloud storage, and produces beautiful output. Install it from mermd.tech and start viewing your diagrams properly.