JSON Formatter & Validator — Free Online JSON Beautifier
Format, validate, minify, repair, and explore JSON data. Fix malformed JSON automatically, navigate with a collapsible tree view, and search within your data. Works with any valid JSON input. 100% client-side — your data stays private.
How to Use the JSON Formatter
- Paste your JSON in the left panel — it auto-formats as you type.
- Switch to Tree view to collapse/expand nested objects and arrays.
- Use "Repair" to auto-fix trailing commas, single quotes, and comments.
- Upload a file by dragging it onto the input area or clicking the upload icon.
- Search for any key or value across the entire JSON structure.
- Download the formatted output as a .json file with one click.
Why Use This JSON Formatter
API responses, config files, and log entries often arrive as unreadable single-line JSON strings. This formatter makes them human-readable with proper indentation and syntax highlighting — so you can actually understand the structure.
Beyond basic formatting, the Tree view lets you navigate deeply nested JSON by collapsing branches, while the Repair function automatically fixes common issues like trailing commas and single quotes. The search feature helps you find any key or value instantly in large payloads.
Frequently Asked Questions
Most common causes: trailing commas (not allowed in JSON, but common in JavaScript), unquoted keys, single quotes instead of double quotes, or missing commas between properties. The error message will tell you the line and character where the issue was detected. Use the "Repair" button to auto-fix many of these issues.
The Repair function handles: trailing commas before closing brackets/braces, single quotes converted to double quotes, JavaScript-style comments removed, unquoted keys quoted, and undefined values converted to null. It shows you what was fixed so you can verify the changes.
Pretty shows formatted, syntax-highlighted JSON text. Tree shows a collapsible, interactive tree where you can expand/collapse branches — ideal for navigating large or deeply nested JSON. Click any key to expand its children.
The tool works entirely in your browser, so it's limited by your browser's memory. For most use cases (API responses, config files), you won't hit any limits. Files over 100MB may slow down — for those, use a desktop tool instead.
This tool validates standard JSON (RFC 8259). JSON5 features like comments, trailing commas, and unquoted keys will be flagged as errors — but the Repair button will fix most of them. For full JSON5 support, use the Repair button first to convert to standard JSON.
Use Cases
Pretty-Printing API Responses
Format minified JSON from API responses to make them readable and easier to analyze.
Debugging Malformed JSON
Identify and repair broken JSON syntax with auto-repair for trailing commas, quotes, and more.
Repairing Broken JSON
Fix malformed JSON from log files and error output with automatic syntax correction.
Exploring Nested Structures
Navigate deeply nested JSON objects with collapsible tree view and instant search.
Validating Config Files
Verify that JSON configuration files are valid before deploying to production environments.