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ClearJSON

npm version Chrome Web Store License

Privacy-first browser JSON viewer. Zero tracking. Fully local. Plus an MCP server for AI agents.

ClearJSON is a Chrome extension that automatically detects and formats JSON responses in your browser. Built in response to the JSON Formatter controversy — we will never inject ads, track you, or sell your data.

MCP Server (New!)

For AI agents (Claude Code, etc.): npx -y clearjson-mcp

{
  "mcpServers": {
    "clearjson": {
      "command": "npx",
      "args": ["-y", "clearjson-mcp"]
    }
  }
}

10 tools — format, validate, search, JSONPath query, deep diff, convert (CSV/TSV/YAML/TypeScript), plus license management. The only large-file-safe JSON MCP server. Available on npm and mcp.so. See AGENT_FIRST.md for the full rationale.

Related MCP server: agent-utils-mcp

Features

Free (forever)

  • ✅ Auto-detect & format JSON/JSON-LD/JSON:API/NDJSON

  • ✅ Collapsible tree view with indent guides

  • ✅ Syntax highlighting (strings, numbers, booleans, null)

  • ✅ 10 themes (Dark, Light, Sepia, Monokai, Dracula, Nord, One Dark, Solarized Light, GitHub, High Contrast)

  • ✅ System-follow theme switching

  • ✅ Click-to-copy values, right-click for JSONPath

  • ✅ Auto-detected links (clickable) and image previews (hover)

  • ✅ Line numbers in raw view

  • ✅ Stats bar (node count, depth, file size, parse time)

  • ✅ Keyboard shortcuts ([ collapse, ] expand, D theme, R raw, Enter search nav)

  • ✅ Standalone viewer (paste JSON, drag-and-drop, file load)

  • ✅ URL exclusion list (regex patterns)

  • ✅ 100% local processing — zero network requests

Pro ($29 lifetime)

  • 💰 Large file virtual scrolling (100MB+ without freezing)

  • 💰 Advanced search (regex, match highlighting, result navigation)

  • 💰 JWT auto-decode (header + payload inline, expiry detection)

  • 💰 Multi-format export (CSV, TSV, YAML, TypeScript types with recursive inference)

  • 💰 30 premium themes (Catppuccin, Tokyo Night, Gruvbox, Nord, Dracula, Monokai…)

  • 💰 Custom keyboard shortcuts (6 configurable bindings)

Install

Chrome Web Store

Install ClearJSON Free

Load Unpacked (Development)

  1. Clone this repo

  2. Go to chrome://extensions/

  3. Enable "Developer mode"

  4. Click "Load unpacked" and select the project folder

Project Structure

clearjson/
├── manifest.json              # Chrome Extension manifest (MV3)
├── server/                    # License server (Cloudflare Worker + D1)
│   ├── src/index.js           # API: verify/generate/webhook/admin
│   ├── schema.sql             # D1 database schema
│   └── wrangler.toml          # Worker config
├── clearjson-mcp/             # MCP server (npm: clearjson-mcp)
│   ├── package.json
│   ├── src/
│   │   ├── index.js           # MCP entry point (stdio transport)
│   │   ├── core/              # Core logic (parser, exporter, license)
│   │   └── tools/             # 7 JSON tools + 3 license tools
│   ├── tests/                 # 49 MCP unit tests
│   └── README.md
├── src/
│   ├── content/
│   │   ├── content.js         # Content script (JSON detection + viewer injection)
│   │   └── content.css        # Base styles + CSS variable theming
│   ├── viewer/
│   │   ├── viewer.html        # Standalone viewer page
│   │   └── viewer.js          # Viewer logic
│   ├── popup/
│   │   ├── popup.html         # Extension toolbar popup
│   │   ├── popup.js
│   │   └── popup.css
│   └── utils/
│       ├── parser.js          # JSON detection + parsing
│       ├── tokenizer.js       # Syntax highlighting tokenizer
│       ├── themes.js          # 30 theme definitions
│       ├── license.js         # Pro license system
│       ├── export.js          # CSV/TSV/YAML/TypeScript export
│       ├── stream-parser.js   # Web Worker streaming parser
│       ├── virtual-tree.js    # Virtual scrolling tree view
│       └── tree.js            # Standard tree view renderer
├── tests/                     # 136 unit tests (Node built-in runner)
│   ├── helpers/setup.js
│   ├── test-parser.js
│   ├── test-tokenizer.js
│   ├── test-jwt.js
│   ├── test-license.js
│   └── test-export.js
├── test-data/                 # Test data + automation scripts
│   ├── complex-api-response.json
│   ├── jwt-test.json
│   ├── users-array.json
│   ├── large-array.json       # 2.2 MB for Pro gate testing
│   ├── server.js              # Local test server (port 8765)
│   ├── run-checklist.js       # 130-item static analysis
│   ├── browser-test.js        # 21-item browser automation
│   └── TEST-CHECKLIST.md      # 43-item manual checklist
├── icons/
│   ├── icon.svg
│   ├── icon16.png
│   ├── icon48.png
│   └── icon128.png
└── README.md

Development

# For development, load the extension unpacked:
# 1. chrome://extensions/ → Developer mode ON
# 2. Load unpacked → select the project root
# 3. Edit files and click refresh on the extension card

# Run unit tests (zero dependencies, Node 18+):
npm test                    # 136 tests (Chrome extension)
cd clearjson-mcp && npm test   # 49 tests (MCP server)

# Run static analysis checklist (130 checks):
node test-data/run-checklist.js

# Run browser automation tests (requires puppeteer):
node test-data/browser-test.js

# Start local test server (Pro auto-enabled on localhost:8765):
node test-data/server.js

Current Status (v1.1.1 — live on CWS)

All features implemented. Pro available via Creem ($29 lifetime). 136 unit tests passing. MCP server v1.1.0 published to npm.

See STATUS.md for full project state, architecture decisions, and release checklist.

Privacy

ClearJSON processes everything locally. We promise:

  • ❌ No data sent anywhere

  • ❌ No analytics or telemetry

  • ❌ No tracking

  • ❌ No ads

  • ❌ No accounts

  • ❌ No third-party scripts

Our permissions are minimal:

  • storage — save your theme preference

  • activeTab — format JSON in the current tab

  • Host permissions — needed only to detect JSON content type; no page content is read on non-JSON pages

Links

Why "ClearJSON"?

After the original JSON Formatter (2M+ users, 10 years open source) was sold and started injecting ads and tracking users, developers needed a trustworthy alternative. ClearJSON is built to be that alternative with a sustainable Pro model that respects users instead of exploiting them.

Install Server
A
license - permissive license
A
quality
B
maintenance

How are these scores calculated?

Maintenance

–Maintainers
–Response time
–Release cycle
–Releases (12mo)
Commit activity

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