RFC 8259 · Client-side · Free JSON Tools
Format, Validate, Beautify & Minify JSON Online
The best free JSON formatter and validator for developers. Format JSON, validate syntax, beautify, minify, debug, and view JSON tree. Paste, upload, or drop a file. Everything runs in your browser — no data leaves your device.
Everything you need to work with JSON
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JSON Beautifier & Minifier
Pretty-print and beautify JSON with 2/4/tab indentation, or minify JSON to the smallest valid representation.
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JSON Validator & Syntax Checker
Validate JSON with precise line and column errors. Lint JSON and get actionable suggestions for trailing commas, unquoted keys, and RFC 8259 compliance.
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JSON Tree View & Explorer
Virtualized JSON tree viewer with expand/collapse, path breadcrumbs, and fast key/value search. Navigate and explore complex JSON structures.
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JSON Diff Viewer
Side-by-side comparison and diff view of your original and formatted JSON output for effortless review.
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Detailed JSON Statistics
JSON parser statistics: keys, objects, arrays, depth, characters, lines, file size, and estimated memory footprint.
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JSON Editor & Keyboard Navigation
Full-featured JSON editor with command palette, discoverable shortcuts, keyboard-first operation, and full keyboard navigation from paste to copy.
Why developers pick JSON Formatter Pro
Private & Secure
No backend server for your JSON data. Zero telemetry, no data collection, no third-party scripts. Your JSON never leaves your device.
Lightning Fast
JSON parsing runs off the main thread in a Web Worker. Tree view is virtualized for instant loading of large JSON files.
Accessible & Inclusive
WCAG 2.2 AA compliant JSON tool. Keyboard-first, reduced-motion friendly, full accessibility support for all users.
Works Offline
Free JSON formatter that works offline after the first load. No CDNs, no fonts fetched at runtime, fully self-contained.
Frequently asked questions
Is my JSON sent to a server? ＋
No. All parsing, formatting, and validation happens in your browser. The tool has zero backend for user data and no network requests are made with your content.
What's the largest file I can format? ＋
Uploads are capped at 50 MB. Files over 5 MB show a confirmation prompt because parsing and rendering may briefly be slower on lower-end hardware. Formatting itself runs off the main thread in a Web Worker.
How do I fix 'Unexpected token' or similar errors? ＋
The status bar shows the exact line, column, and a plain-English suggestion. Common causes are trailing commas, single quotes instead of double quotes, unquoted property names, and stray comments — none of which are permitted by RFC 8259.
Can I use this offline? ＋
Yes. Once the page has loaded, all functionality — including the editor, worker, and views — runs entirely offline. No third-party scripts or fonts are loaded.
What's the difference between Minify and Format? ＋
Format (or Beautify) inserts whitespace and indentation so the JSON is easy to read. Minify strips every non-essential character to produce the smallest valid representation, which is useful for storage or transmission.
Does the tool support JSON with comments (JSONC) or trailing commas? ＋
It validates strict RFC 8259 JSON, so comments and trailing commas are reported as syntax errors. This is intentional — most APIs and configuration systems require strict JSON.
Are my settings and last input remembered between visits? ＋
Preferences (theme, indentation, transforms) and up to 512 KB of your last input are stored in your browser's localStorage. Nothing leaves your device. Use the Clear action to wipe the current buffer.
Is the tool accessible? ＋
Yes. The interface targets WCAG 2.2 AA — full keyboard navigation, ARIA landmarks, visible focus rings, reduced-motion support, and high-contrast light and dark themes.
How do I pretty print JSON? ＋
Simply paste or upload your JSON, and our formatter will automatically beautify it with proper indentation. You can choose between 2-space, 4-space, or tab indentation.
How can I validate my JSON online? ＋
Our JSON validator checks your code against RFC 8259 standards and reports any syntax errors with exact line and column numbers. It provides helpful suggestions for common mistakes.
What is JSON minification and when should I use it? ＋
JSON minification removes all unnecessary whitespace to reduce file size. It's useful for reducing API payloads, shrinking configuration files, and optimizing storage and transmission speed.
Can I convert JSON to other formats? ＋
Our formatter specializes in JSON formatting and validation. For conversions to XML, CSV, YAML, or other formats, you'll need a format conversion tool.
How do I debug JSON syntax errors? ＋
The JSON debugger shows you the exact location of syntax errors with helpful suggestions. Common issues like trailing commas, unquoted keys, and quote mismatches are highlighted.
Is there a free JSON formatter with no registration needed? ＋
Yes! Our JSON formatter is completely free with no sign-up, registration, or login required. It's also free from ads and tracking.
Can I view JSON in tree format? ＋
Yes. Our JSON tree view allows you to explore your JSON structure visually with expandable nodes, breadcrumb navigation, and fast key search.