/desktop-storage-electron

name: desktop-storage-electron
description: Persistent storage, SQLite databases, and credential management in Electron apps

Electron Storage & Credentials

> **Quick Guide:** Use `electron-store` for typed JSON preferences (small key-value config with schema validation, migrations, and file watching). Use `better-sqlite3` for structured/relational data or anything beyond simple key-value (synchronous, WAL mode, transactions). Use `safeStorage` for encrypting secrets like tokens and API keys via the OS keychain -- it replaces the deprecated `keytar`. All persistent data belongs under `app.getPath("userData")`. Never store secrets in plain JSON files.

---

<critical_requirements>

CRITICAL: Before Using This Skill

> **All code must follow project conventions in CLAUDE.md** (kebab-case, named exports, import ordering, `import type`, named constants)

**(You MUST use `safeStorage.encryptString()` / `safeStorage.decryptString()` for secrets -- never store tokens, API keys, or passwords in plain text or in electron-store without OS-level encryption)**

**(You MUST store all persistent data under `app.getPath("userData")` -- never write to the app installation directory, which is replaced on updates)**

**(You MUST enable WAL mode (`PRAGMA journal_mode = WAL`) when using better-sqlite3 -- it prevents readers from blocking writers and avoids SQLITE_BUSY errors in multi-window apps)**

**(You MUST call `safeStorage.isEncryptionAvailable()` before encrypting -- it returns false before the app `ready` event and on some Linux configurations)**

**(You MUST rebuild better-sqlite3 for Electron's Node.js version using `@electron/rebuild` -- mismatched native bindings crash the app)**

</critical_requirements>

---

**Auto-detection:** electron-store, better-sqlite3, safeStorage, app.getPath, userData, encryptString, decryptString, isEncryptionAvailable, lowdb, JSONFilePreset, persistent storage, credential storage, keytar replacement, electron config, electron preferences, electron database

**When to use:**

• Persisting user preferences and app configuration
• Storing structured or relational data locally
• Encrypting tokens, API keys, or other secrets
• Choosing between storage solutions for an Electron app
• Migrating stored data between app versions
• Working with `app.getPath()` standard directories

**When NOT to use:**

• Choosing a UI framework or styling for the renderer (separate skill)
• IPC communication patterns between main and renderer (separate concern)
• Packaging and distribution concerns (separate concern)
• Server-side or cloud storage

**Key patterns covered:**

• electron-store: typed config, schema validation, migrations, encryption, watching
• better-sqlite3: WAL mode, prepared statements, transactions, native module rebuild
• safeStorage: OS keychain encryption for secrets, replacing keytar
• lowdb: lightweight JSON database for medium-complexity data
• Storage path conventions using `app.getPath()`
• Credential storage best practices

---

<philosophy>

Philosophy

Electron apps have access to the full filesystem but should store data in OS-designated locations. The right storage solution depends on data shape and sensitivity:

**Preferences and small config** (theme, window bounds, feature flags): `electron-store` writes a single JSON file atomically. It is read and written in full on every change, so it is only appropriate for small data (under ~1MB).

**Structured or queryable data** (chat history, project metadata, analytics): `better-sqlite3` provides a synchronous SQLite database with ACID transactions. It handles concurrent reads via WAL mode and scales to gigabytes.

**Secrets** (OAuth tokens, API keys, passwords): `safeStorage` uses the OS keychain (macOS Keychain, Windows DPAPI, Linux secret service) to encrypt strings. The encrypted buffer can be stored in electron-store or a file -- only your app can decrypt it on the same machine and user account.

**Medium-complexity JSON data** (todo lists, small document stores): `lowdb` provides a file-backed JavaScript object with native array methods. Simpler than SQLite for JSON-shaped data that does not need relational queries.

**Key principle:** Storage runs in the **main process**. Renderers request data via IPC. Never give renderers direct filesystem or database access.

</philosophy>

---

<patterns>

Core Patterns

Pattern 1: electron-store -- Typed Preferences

Use for small key-value configuration that persists across sessions. Supports schema validation, defaults, and migrations.

import Store from "electron-store";

interface AppSettings {
  theme: "light" | "dark" | "system";
  windowBounds: { width: number; height: number; x?: number; y?: number };
  recentFiles: string[];
  fontSize: number;
}

const DEFAULT_WIDTH = 1200;
const DEFAULT_HEIGHT = 800;
const MIN_FONT_SIZE = 8;
const MAX_FONT_SIZE = 72;
const DEFAULT_FONT_SIZE = 14;

const store = new Store<AppSettings>({
  defaults: {
    theme: "system",
    windowBounds: { width: DEFAULT_WIDTH, height: DEFAULT_HEIGHT },
    recentFiles: [],
    fontSize: DEFAULT_FONT_SIZE,
  },
  schema: {
    fontSize: {
      type: "number",
      minimum: MIN_FONT_SIZE,
      maximum: MAX_FONT_SIZE,
    },
  },
});

**Why good:** Type-safe generic parameter ensures `.get()` and `.set()` are checked at compile time, named constants for all limits, schema rejects invalid values at write time

See [examples/core.md](examples/core.md) for migrations, file watching, dot-notation access, and renderer integration via IPC.

---

Pattern 2: better-sqlite3 -- Local Database

Use for structured data that benefits from queries, indexes, or transactions. Always enable WAL mode.

import Database from "better-sqlite3";
import { app } from "electron";
import path from "node:path";

const DB_FILE = "app-data.db";

const db = new Database(path.join(app.getPath("userData"), DB_FILE));

// Performance pragmas -- set once at connect