JSON Viewer for macOS

A fast, lightweight, native macOS application recreating and elevating the classic online JSON Viewer and Formatter (jsonviewer.stack.hu).

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📸 Overview & Split Mode

Experience real-time JSON editing and hierarchical exploration side-by-side:

Split Mode: Monospace Editor (left), Tree Hierarchy with full-width expanded text (center), and Interactive Property Inspector with jump navigation (right).

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✨ Features & Walkthrough

1. Hierarchical Tree Viewer with Expandable Full-Width Text

Explore deep JSON structures with collapsible nodes, color-coded type badges, and dynamic full-width multi-line textareas for large text fields:

• 🏷️ Type Badges matching jsonviewer.stack.hu:
  • 🔵 String (key : "value")
  • 🟢 Number (key : 123)
  • 🟡 Boolean (key : true)
  • 🔴 Null (key : null)
  • 🟣 Object / Array (key {N} / key [N])
• 📖 Expandable Big Text:
  • Automatic detection for long strings (> 40 characters or newlines).
  • Visual cue badge [ ▾ expand ] and text.badge.plus icon.
  • Full-Width Responsive Textarea: Stretches across the full width of the tree panel and wraps smoothly.
  • Includes a quick Copy button with animated "Copied!" confirmation, character count badge, and native text selection (.textSelection(.enabled)).
• 🖱️ Context Menus: Right-click any tree node to Expand, Expand All, Collapse, Collapse All, Copy Value, Copy Key, Copy JSON Path (e.g. $.users[0].address.city), or Copy Subtree as JSON.

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2. Interactive Property Inspector & Jump Navigation

Inspect element properties in a 2-column table with click-to-jump tree synchronization:

• 🔗 Clickable Property Names: Clicking on any property name in the grid (e.g. 23 or name) instantly jumps to, selects, and scrolls to that element in the tree.
• ⚡ Auto-Reveal: Ancestor nodes of target items are automatically unfolded in the tree view.
• 🧭 Breadcrumb Navigation: Header back button [ < Parent ] allows easy navigation back up the object tree.
• 🔍 In-Grid Search Filter: Quickly filter through thousands of properties in large objects.
• 📐 Expandable Grid Values: Built-in [ ▾ more ] / [ ▴ less ] toggles for long values within grid cells.

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3. Native Text Editor & Transformations (Middle Tab)

A full-featured code editor with instant syntax feedback and rich serialization tools:

• ⚡ Editor Actions & Transformations:
  • Format (Beautify): Prettifies JSON with configured indentation (2 spaces, 4 spaces, tabs).
  • Minify: Compresses JSON to a single line without spaces.
  • Stringify: Serializes JSON or text into an escaped JSON string literal with forward slash escaping (\/) and quote escaping (\").
  • Unescape: Unwraps stringified JSON or decode escape characters (\/, \", \\, \n) back into clean formatted JSON.
  • Multi-Format Copy: Copy as Beautified JSON, Minified JSON, Stringified JSON, or Python Object literal.
  • Paste / Clear: Fast clipboard integration and buffer reset.
• 🛡️ Syntax Validation: Real-time error detection reporting exact line and column numbers.
• 📊 Status Bar: Real-time line and character counter.
• 📁 Native macOS File Handling: Open (Cmd+O) and Save (Cmd+S) .json files.

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4. Multi-Format Copy & Python Dictionary Serialization

Copy your JSON in whatever format you need directly from the Viewer toolbar, Text Editor, or context menus:

• 📋 Copy Beautified JSON: Configurable indentation (2-space, 4-space, tabs).
• ⚡ Copy Minified JSON: Single-line compact JSON.
• 🔤 Copy as Stringified JSON: Escaped string literal with quotes (\") and forward slashes (\/).
• 🐍 Copy as Python Dictionary: Native Python dictionary/list representation using True, False, None, and single-quoted strings.
• 🔄 Automatic Python Dictionary to JSON Conversion: Paste or type any Python dictionary into the editor ({'key': 'value', 'flag': True, 'empty': None}) and it is automatically converted into valid, formatted JSON.

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5. Settings Page & Keyboard Shortcuts Cheatsheet

• ⚙️ Settings (⌘,): Configure indentation (2 spaces, 4 spaces, tabs), forward slash escaping (\/), alphabetical key sorting, auto-unwrapping of stringified JSON, editor font size, and word wrapping.
• ⌨️ Keyboard Shortcuts Cheatsheet (?): Press ? anytime outside text fields or ⌘ ? anywhere to open a beautiful categorized shortcuts overlay with instant search.

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⚡ Performance & Scale

• Virtualized Rendering: High-performance lazy row rendering capable of smoothly navigating datasets with 15,840+ items and 5MB+ payloads with zero UI lag.
• Pure Swift Engine: Zero third-party runtime dependencies; built exclusively with AppKit and SwiftUI.

📦 Installation (Pre-built App)

1. Download JSONViewer-macOS.zip from the GitHub Releases.
2. Double-click the downloaded .zip file to extract JSONViewer.app.
3. Drag JSONViewer.app into your /Applications folder.

[!NOTE] First-time Opening on macOS (Gatekeeper): Since this is an open-source application without an Apple Developer ID certificate:

• Right-click (or Control-click) JSONViewer.app and select Open, then click Open in the prompt.
• Alternatively, run this command once in Terminal:

  xattr -cr /Applications/JSONViewer.app
  

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🚀 Building and Running from Source

Prerequisites

• macOS 13.0 (Ventura) or later
• Xcode Command Line Tools (xcode-select --install)

Quick Run via Swift PM

swift run

Build & Install to /Applications

./build_app.sh install

This compiles the release binary, creates the iconset, code-signs the app, installs it to /Applications/JSONViewer.app, and launches it.

Build macOS App Bundle

./build_app.sh run

This builds build.noindex/JSONViewer.app and launches it.

Run Automated Test Suite

swift run JSONViewerTests

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⌨️ Keyboard Shortcuts

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📜 Credits

Inspired by the original online JSON Viewer and Formatter by Gabor Turi.
Rebuilt natively for macOS in modern Swift.