Free Online JSONPath Expression Tester

A high-performance, single-file browser utility designed for developers and data engineers to validate, debug, and extract data from JSON objects using JSONPath queries. This application provides an immediate, visual feedback loop for writing complex data-traversal expressions.

Core Features

• Real-time Evaluation: The results update instantly as you type your JSON data or modify your JSONPath query.
• Syntax Highlighting: Integrated code editing experience with syntax error detection for both JSON inputs and JSONPath expressions.
• Error Reporting: Clear, human-readable error messages for invalid JSON structures or syntax-heavy path expressions.
• Privacy-First Architecture: Operates 100% in-memory. Zero server-side processing and zero persistent storage usage.
• Responsive Interface: A split-pane desktop layout that gracefully transforms into a stacked mobile layout for on-the-go debugging.

UI/UX Specification

• Layout:
  • Header: Clean, minimalist title with a descriptive tagline.
  • Input Area: Two primary textareas side-by-side (Desktop) or stacked (Mobile). Left pane for 'JSON Data', Right pane for 'JSONPath Query'.
  • Results Output: A dedicated, read-only display area for the evaluation results, formatted as a syntax-highlighted JSON block.
  • Controls: A 'Format JSON' button to beautify inputs and a 'Clear All' button.
• Visual Design (Light Mode Only):
  • Palette: Crisp off-white backgrounds (#F9FAFB), slate-gray text (#374151), accent blues (#2563EB) for interactive buttons, and semantic error-red (#DC2626) for validation issues.
  • Typography: Inter or system-sans fonts for extreme readability.
  • Shadows: Soft, diffused drop shadows on input panels to create a modern "card" aesthetic.
  • Animations: Subtle transition effects (150ms ease-in-out) for panel focus states and results updates.

Developer Directives & Constraints

1. Environment: Must be a single index.html file. Use CDN imports for dependencies (e.g., a lightweight JSONPath library like jsonpath-plus or jsonpath and a syntax highlighter like Prism.js).
2. Sandbox Compliance:
   • NO localStorage, sessionStorage, IndexedDB, or cookies.
   • NO alert(), confirm(), or prompt(). All UI notifications must use custom HTML modal overlays.
   • All links must use target="_blank" rel="noopener noreferrer".
3. Formatting: Use native CSS Flexbox/Grid for the layout. Ensure the application is responsive; the editor panes should handle window resizing without overflow issues.
4. Performance: Debounce all input listeners (300ms) to ensure smooth typing performance during data evaluation.