Architecture

Trilium Notes is a hierarchical note-taking application built as a TypeScript monorepo. It supports multiple deployment modes (desktop, server, mobile web) and features advanced capabilities including synchronization, scripting, encryption, and rich content editing.

Key Characteristics

• Monorepo Architecture: Uses pnpm workspaces for dependency management
• Multi-Platform: Desktop (Electron), Server (Node.js/Express), and Mobile Web
• TypeScript-First: Strong typing throughout the codebase
• Plugin-Based: Extensible architecture for note types and UI components
• Offline-First: Full functionality without network connectivity
• Synchronization-Ready: Built-in sync protocol for multi-device usage

Technology Stack

• Runtime: Node.js (backend), Browser/Electron (frontend)
• Language: TypeScript, JavaScript
• Database: SQLite (better-sqlite3)
• Build Tools:
  • Client: Vite,
  • Server: ESBuild (bundling)
  • Package manager: pnpm
• UI Framework: Custom widget-based system (vanilla HTML, CSS & JavaScript + jQuery), in the process of converting to React/Preact.
• Rich Text: CKEditor 5 (customized)
• Code Editing: CodeMirror 6
• Desktop: Electron
• Server: Express.js

Main architecture

Trilium follows a client-server architecture even in desktop mode, where Electron runs both the backend server and frontend client within the same process.

graph TB
    subgraph Frontend
        Widgets[Widgets
System]
        Froca[Froca
Cache]
        UIServices[UI
Services]
    end
    
    subgraph Backend["Backend Server"]
        Express[Express
Routes]
        Becca[Becca
Cache]
        ScriptEngine[Script
Engine]
        Database[(SQLite
Database)]
    end
    
    Widgets -.-> API[WebSocket & REST API]
    Froca -.-> API
    UIServices -.-> API
    API -.-> Express
    API -.-> Becca
    API -.-> ScriptEngine
    Becca --> Database
    Express --> Database
    ScriptEngine --> Database

Deployment Modes

1. Desktop Application
   • Electron wrapper running both frontend and backend
   • Local SQLite database
   • Full offline functionality
   • Cross-platform (Windows, macOS, Linux)
2. Server Installation
   • Node.js server exposing web interface
   • Multi-user capable
   • Can sync with desktop clients
   • Docker deployment supported
3. Mobile Web
   • Optimized responsive interface
   • Accessed via browser
   • Requires server installation

Monorepo Structure

Trilium uses pnpm workspaces to manage its monorepo structure, with apps and packages clearly separated.

trilium/
├── apps/                    # Runnable applications
│   ├── client/             # Frontend application (shared by server & desktop)
│   ├── server/             # Node.js server with web interface
│   ├── desktop/            # Electron desktop application
│   ├── web-clipper/        # Browser extension for web content capture
│   ├── db-compare/         # Database comparison tool
│   ├── dump-db/            # Database export tool
│   ├── edit-docs/          # Documentation editing tool
│   ├── build-docs/         # Documentation build tool
│   └── website/            # Marketing website
│
├── packages/               # Shared libraries
│   ├── commons/           # Shared interfaces and utilities
│   ├── ckeditor5/         # Custom rich text editor
│   ├── codemirror/        # Code editor customizations
│   ├── highlightjs/       # Syntax highlighting
│   ├── ckeditor5-admonition/     # CKEditor plugin: admonitions
│   ├── ckeditor5-footnotes/      # CKEditor plugin: footnotes
│   ├── ckeditor5-keyboard-marker/# CKEditor plugin: keyboard shortcuts
│   ├── ckeditor5-math/           # CKEditor plugin: math equations
│   ├── ckeditor5-mermaid/        # CKEditor plugin: diagrams
│   ├── express-partial-content/  # HTTP partial content middleware
│   ├── share-theme/              # Shared note theme
│   ├── splitjs/                  # Split pane library
│   └── turndown-plugin-gfm/      # Markdown conversion
│
├── docs/                   # Documentation
├── scripts/                # Build and utility scripts
└── patches/                # Package patches (via pnpm)

Package Dependencies

The monorepo uses workspace protocol (workspace:*) for internal dependencies:

desktop → client → commons
server  → client → commons
client  → ckeditor5, codemirror, highlightjs
ckeditor5 → ckeditor5-* plugins

Security summary

Encryption System

Per-Note Encryption:

• Notes can be individually protected
• AES-128-CBC encryption for encrypted notes.
• Separate protected session management

Protected Session:

• Time-limited access to protected notes
• Automatic timeout
• Re-authentication required
• Frontend: protected_session.ts
• Backend: protected_session.ts

Authentication

Password Auth:

• PBKDF2 key derivation
• Salt per installation
• Hash verification

OpenID Connect:

• External identity provider support
• OAuth 2.0 flow
• Configurable providers

TOTP (2FA):

• Time-based one-time passwords
• QR code setup
• Backup codes

Authorization

Single-User Model:

• Desktop: single user (owner)
• Server: single user per installation

Share Notes:

• Public access without authentication
• Separate Shaca cache
• Read-only access

CSRF Protection

CSRF Tokens:

• Required for state-changing operations
• Token in header or cookie
• Validation middleware

Input Sanitization

XSS Prevention:

• DOMPurify for HTML sanitization
• CKEditor content filtering
• CSP headers

SQL Injection:

• Parameterized queries only
• Better-sqlite3 prepared statements
• No string concatenation in SQL

Dependency Security

Vulnerability Scanning:

• Renovate bot for updates
• npm audit integration
• Override vulnerable sub-dependencies