JSON Formatter & Validator

Free JSON formatter and validator — lossless (never corrupts big numbers), with precise line-and-column errors, duplicate-key detection, a one-click repair for trailing commas and comments, a collapsible tree view, search, sort keys, minify and download.

JSON Formatter — Beautify, Validate, and Minify JSON Instantly

Raw JSON from APIs, log files, and databases is a single line of nested braces and brackets that is nearly impossible to read. When you are debugging a webhook payload, reviewing an API response, or checking a config file, you need it formatted with proper indentation and syntax highlighting so you can actually see the structure — without the tool quietly changing your data along the way.

This formatter validates and beautifies JSON, highlights it in colour, shows a collapsible tree, and minifies it back to one line. Crucially, it does this losslessly — a 20-digit ID stays a 20-digit ID — and when something is wrong it points at the exact line and column. No signup, no installation, no cost.

Accuracy that ordinary formatters miss

It never corrupts your numbers. A formatter built on the browser's JSON.parse turns 12345678901234567890 into 12345678901234567000 — silent data loss for large IDs, coordinates and financial values. This one keeps every number exactly as written, because it parses with its own engine and re-emits the original digits.
Errors pinned to line and column. Instead of a vague browser message, you get the exact spot — "Expected ',' or ']' at line 3, column 21" — with the offending line and a caret pointing right at it.
Duplicate keys are flagged, not dropped. {"a":1,"a":2} quietly loses the first value in most tools. Here you get a warning naming the key and its line.
One-click repair. Paste JSON with trailing commas, // or /* */ comments, single quotes or unquoted keys, and Repair rewrites it as clean, strict JSON.
Key order is preserved. Formatting through a plain JavaScript object reshuffles integer-like keys ("2" before "10"); this keeps your keys in the order you wrote them.

How to Format JSON

Paste your raw JSON, click format, and get clean, readable output with proper indentation and highlighting.

1. Paste JSON

Paste raw JSON from an API response, log file, database export, or configuration file. Upload a .json file if you prefer.

2. Validate

The formatter checks for syntax errors and reports the exact line and position of any problem. Valid JSON is formatted instantly.

3. Beautify or Minify

Format with 2-space or 4-space indentation for readability, or minify to a single compact line for production.

4. Copy or Download

Copy the formatted output to your clipboard or download as a .json file. Share with teammates or paste into your code.

All processing happens in your browser. No JSON data is sent to any server. Safe for API keys, tokens, and sensitive payloads.

Features for Developers

Syntax Highlighting

Keys, strings, numbers, booleans, and null values are colour-coded for instant visual parsing.

Collapse Nodes

Click to collapse nested objects and arrays. Focus on the section you are debugging without scrolling through thousands of lines.

Error Detection

Syntax errors are highlighted with the exact line number and character position. Missing commas, unmatched brackets, and trailing commas are caught instantly.

Minify

Compress formatted JSON back to a single line. Remove all whitespace for minimal file size in production payloads.

Search and Filter

Search for specific keys or values within large JSON structures. Find what you need without manually scanning the tree.

Private and Free

Runs in your browser. No data leaves your device. Safe for sensitive API responses and configuration files.

JSON Formatter — FAQs

Yes. The formatter handles JSON files up to several megabytes in size. Very large files are parsed and formatted with streaming techniques to avoid browser memory issues.

Both, depending on what you need. By default it validates strictly and points to the exact location of any error so you can fix it yourself. But the Repair button (and the "Lenient parse" option) accepts the near-JSON people actually paste — trailing commas, // and /* */ comments, single-quoted strings, unquoted keys — and rewrites it as clean, strict JSON. What it will not do is guess at genuinely broken structure like a missing bracket; for that it shows you the line and column so the fix is obvious.

Yes. All processing happens locally in your browser. No JSON data is ever transmitted to a server. This makes it safe to use with API keys, tokens, and other sensitive data.

Most formatters run your text through JavaScript's JSON.parse, and JavaScript stores every number as a 64-bit float. That can hold integers exactly only up to about 9 quadrillion (2⁵³). Anything bigger — a 19-digit Twitter/X ID, a Snowflake ID, a database bigint — gets rounded: 12345678901234567890 comes back as 12345678901234567000, and the tool re-prints the wrong value with no warning. High-precision decimals lose their tail the same way. This tool parses numbers as text and prints them back exactly as you typed them, so nothing is ever silently altered.

Paste it and format. If it is invalid, the output panel names the problem in plain language — a missing comma, an unclosed bracket, a trailing comma, an unquoted key — and gives the exact line and column, with the offending line shown and a caret pointing at the character. That is usually enough to fix it in seconds. The most common causes are a comma after the last item in an object or array, a missing comma between two items, and property names that are not wrapped in double quotes.

Yes, completely free. No signup, no ads.

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