Formatter Validator Minifier Escape / Unescape JSON ↔ String JSON ↔ YAML JSON → CSV NDJSON / JSON Lines JSON → Types JSON ↔ XML JSON Diff JSON Patch Canonicalize (RFC 8785) Schema Validator Schema Generator JSONPath Tester JWT Decoder JSON Errors Schemas More Tools
100% Browser-Based · Privacy-First · No Upload

Free Online JSON Formatter & Validator

Pretty-print, validate, and beautify JSON in your browser. Real-time error reporting with exact line and column. The fastest privacy-first JSON tool — your data never leaves your device, no upload, no logging, no signup required.

Input JSON 0 bytes
1
Formatted Output 
Formatted JSON will appear here
What is a JSON Formatter?

What is a JSON Formatter?

A JSON formatter (also called a JSON beautifier or pretty printer) is a tool that takes minified or messy JSON data and reformats it with proper indentation, line breaks, and consistent spacing so humans can read it easily. JSON — short for JavaScript Object Notation — is the most widely used data format on the web today, powering REST APIs, configuration files, NoSQL databases, and countless other systems.

When you receive JSON from an API or pull it from a database, it usually arrives as a single line with no whitespace, designed for efficient transmission rather than human inspection. A JSON formatter takes that compressed string and structures it visually: each key on its own line, nested objects indented, arrays expanded — making it possible to scan, debug, and understand at a glance.

Our online JSON formatter does this and more. Beyond pretty-printing, it validates your JSON against the official RFC 8259 specification, highlights syntax with color coding (keys in blue, strings in green, numbers in orange, booleans in purple), reports any errors with exact line and column numbers, and provides instant stats: byte size, line count, total keys, and maximum nesting depth.

How to format JSON online (step-by-step)

How to format JSON online (step-by-step)

Using our JSON beautifier is straightforward. Here's the complete workflow:

  1. Paste your JSON into the input panel on the left. You can also click Upload to load a .json file from your computer, or simply drag and drop the file onto the input area. There's also a Sample button if you want to try the tool without your own data.
  2. Choose your indent style — 2 spaces (the most common default), 4 spaces (for traditional codebases), or tab characters (for projects that prefer tabs). Most APIs and style guides recommend 2-space indentation.
  3. Click Format, or just wait — the tool auto-formats as you type. The output appears in the right panel with full syntax highlighting.
  4. If your JSON is invalid, you'll see a red error indicator and a message pointing to the exact line and column where parsing failed. Fix the issue and the format applies automatically.
  5. Copy or download the formatted result with one click. The download saves a .json file you can use anywhere.

The entire process happens locally in your browser using your computer's JavaScript engine. No data is uploaded to any server — you can verify this in your browser's Network tab.

When should you format JSON?

When should you format JSON?

JSON formatting is essential in a wide range of development scenarios:

API Debugging API responses

When an API returns a complex nested response, formatting makes it possible to find the field you need. This is the most common use case — every developer working with REST APIs hits this daily.

CFG Reading config files

Many tools store configuration as JSON (package.json, tsconfig.json, .eslintrc.json). When these get checked into git, you want them pretty-printed so changes show up cleanly in diffs.

DB Inspecting database documents

MongoDB, Firebase, DynamoDB, and other NoSQL databases store documents as JSON. Exporting them produces minified blobs that need beautification before review.

LOG Reading structured logs

Modern logging systems emit JSON Lines (JSONL) where each line is a JSON object. Formatting individual log entries reveals the full context of an event.

WS Webhook payloads

Stripe, GitHub, Slack, and other services send JSON webhook payloads. Before writing handler code, you need to see the structure clearly.

EDU Learning JSON

If you're new to JSON, seeing examples pretty-printed teaches the syntax — nested objects, arrays, key-value pairs, data types — much faster than reading the spec.

Why use this JSON formatter instead of others?

Why use this JSON formatter instead of others?

Most online JSON formatters require uploading your data to a server. That's a problem if your JSON contains sensitive information — API keys, personal data, internal company records, or anything regulated. Our tool is fundamentally different:

  • True browser-side processing. Every byte of JSON you paste is parsed by the JavaScript engine inside your browser tab. The website's server never sees your data because there is no server-side processing. Open your browser's Network tab while using the tool — you'll see zero outbound requests carrying your data.
  • Exact error locations. Many JSON validators just tell you "invalid JSON" and force you to find the problem yourself. We extract the parser's error position and convert it to a precise line and column, so you can jump straight to the issue.
  • Real-time validation. The tool re-validates as you type with a 150ms debounce, so you see errors immediately without clicking a button.
  • Works offline. Once the page is loaded, you can disconnect from the internet and the tool keeps working. Useful for handling truly sensitive data on an air-gapped machine.
  • Fast on large files. Native JSON.parse and JSON.stringify are the fastest parsers your browser has access to. We don't reimplement them in JavaScript — we use them directly, so a 10 MB JSON file formats in under a second on modern hardware.
  • Free forever. No signup, no paywall, no usage limits. The site is supported by ads in the page chrome (not in the tool itself).
Common JSON syntax errors and how to fix them

Common JSON syntax errors and how to fix them

If your JSON keeps failing validation, one of these is almost certainly the cause:

, Trailing commas

{"a":1,} is valid JavaScript but invalid JSON. Remove any comma that comes right before a closing brace or bracket. This is the #1 cause of JSON parsing failures.

' Single quotes

JSON requires double quotes for every string and key. Convert {'name':'Ada'} to {"name":"Ada"}. This trips up developers coming from Python or JavaScript.

a Unquoted keys

JSON object keys must always be in double quotes — even simple identifier-like names. {name:"Ada"} fails; {"name":"Ada"} works.

// Comments

JSON does not allow // line comments or /* block comments */. If you have a config file with comments (often called JSONC), strip them before pasting, or use a JSONC-aware parser.

∞ NaN, Infinity, undefined

These values exist in JavaScript but not in JSON. Use null or a string sentinel like "NaN" if you need to represent them.

"\ Unescaped characters

Inside a string, backslashes, double quotes, and control characters must be escaped: \\, \", \n, \t. An unescaped quote inside a string is one of the most common silent errors.

Other JSON tools you might need

Other JSON tools you might need

This formatter is part of a complete suite of free, browser-based JSON utilities:

JSON Validator

Strict RFC 8259 validation with precise error location reporting.

JSON Minifier

Compress JSON to a single line — reduce API payload size by 30-60%.

JSON ↔ YAML Converter

Bi-directional conversion for Kubernetes, GitHub Actions, OpenAPI.

JSON to CSV

Convert arrays of objects to CSV for Excel and Google Sheets.

JSON ↔ XML

Convert between JSON and XML preserving attributes and structure.

JSON Diff

Compare two JSON documents semantically — find what changed.

JSON Schema Validator

Validate JSON against a JSON Schema (Draft 7 / 2019-09 / 2020-12).

JSONPath Tester

Run JSONPath queries on a document — like XPath, but for JSON.

JWT Decoder

Decode JSON Web Tokens — view header, payload, and signature.
Learn more about JSON in our blog

Learn more about JSON in our blog

Want to go deeper? Our blog covers JSON in depth: syntax fundamentals, performance optimization, schema design, security considerations, and language-specific guides for Python, JavaScript, Go, and more.

JSON vs YAML: Which Should You Use?

A detailed comparison of the two most popular structured data formats.

Why is My JSON Invalid? 10 Common Errors

A diagnostic guide to fixing the JSON syntax errors that trip developers up.

JSON Best Practices for API Design

How to structure JSON responses that scale, version cleanly, and stay fast.

View all articles →

27 in-depth guides covering JSON formatting, validation, conversion, and more.
Common questions

FAQ — JSON Formatter

Is the JSON formatter free?
Yes — completely free, with no signup, paywall, or usage limits. The site is supported by ads that appear in the page chrome (header and footer area), never inside the tool itself. There are no premium tiers or feature gates.
Is my JSON data sent to a server?
No. Every byte of JSON you paste stays inside your browser tab. All parsing, formatting, validation, and conversion is done by JavaScript running on your device. You can verify this yourself: open your browser's Developer Tools, switch to the Network tab, and watch what happens when you format JSON. You'll see zero outbound requests carrying your data.
How does the JSON formatter handle large files?
The tool comfortably handles JSON documents up to about 50 MB on modern browsers. Above that, browser memory and rendering performance become limiting factors. For files between 50 MB and 100 MB, expect noticeable lag. For documents above 100 MB, we recommend a command-line tool like jq instead — it streams data and can handle gigabyte-scale files.
What's the difference between formatting (pretty-printing) and minifying JSON?
Formatting (also called pretty-printing or beautifying) adds whitespace — indentation, newlines, and spaces — so JSON is easy for humans to read. Minifying does the opposite: it strips all whitespace to produce the most compact valid JSON. The data itself is identical in both cases; only the whitespace differs. Use formatting for development, debugging, and reading. Use minification for production API responses, storage, and over-the-wire transmission.
Why is my JSON invalid even though it looks fine?
The most common silent causes: (1) a trailing comma before a closing brace or bracket — valid in JavaScript but not JSON; (2) single quotes instead of double quotes; (3) unquoted object keys; (4) comments (JSON doesn't allow them); (5) special values like NaN, Infinity, or undefined; (6) an invisible byte-order mark (BOM) at the start of the file; (7) smart quotes pasted from a word processor instead of straight ASCII quotes. The error message will point to the exact line and column where parsing failed.
Does this work with JSON5 or JSONC (JSON with comments)?
No — we strictly validate against RFC 8259, the official JSON specification. JSON5 is a friendlier superset that allows comments, trailing commas, and unquoted keys; JSONC (JSON with Comments) is used in VS Code config files. If you have JSON5 or JSONC, strip the comments and convert single quotes to double quotes before pasting. We may add JSON5 support as an optional mode in the future.
How is the line and column number determined when JSON is invalid?
When JavaScript's built-in JSON.parse encounters invalid syntax, modern browsers (Chrome 113+, Firefox 115+, Safari 16.4+) include a character position in the error message. We extract that position and walk through the input text counting newlines to convert it into a precise line and column. For older browsers we use multiple fallback strategies — extracting the failing token from the error message and finding it in the source text.
Can I format JSON offline?
Yes. Once the page has loaded, the entire tool runs locally in your browser. You can disconnect from the internet, close the network, and everything keeps working. For truly air-gapped scenarios, you can save the page (Ctrl+S / Cmd+S) and use the saved copy without any network access at all.
What's the maximum JSON depth this tool supports?
JavaScript's JSON.parse has effectively no hard depth limit, but very deep nesting (thousands of levels) can hit the engine's call stack limit and throw Maximum call stack size exceeded. In practice, depth above 200-500 is rare in real JSON and usually indicates a bug in whatever generated it. The tool displays the maximum depth in the output stats so you can spot anomalies.
Does the formatter preserve numeric precision?
JavaScript represents all numbers as 64-bit floats, so integers larger than 2^53 (about 9 quadrillion) lose precision when parsed. This is a JSON-level limitation, not a tool limitation. If your JSON contains huge integer IDs (Twitter snowflake IDs, for example), store them as strings rather than numbers to preserve precision. The formatter will accept the input either way — it just can't restore precision that was already lost during parsing.
Can I share a formatted JSON via URL?
Not directly through this tool — we don't store anything, so there's no server-side ID to link to. For sharing, copy the formatted output and paste it into a gist (gist.github.com), Pastebin, or any other paste service. Avoid sharing JSON that contains secrets via public paste services.
How does this compare to JSONLint, JSON Formatter & Validator, and CodeBeautify?
Functionally similar — all of them format and validate JSON. The key differences: (1) most competitor sites send your JSON to their server for processing; ours doesn't. (2) Our error reporting is line/column precise rather than character-position only. (3) The interface is uncluttered with no ads inside the tool itself. (4) The site loads faster because we don't use heavy frameworks. If privacy and speed matter to you, we'd argue ours is the better choice — but the basic format/validate functionality is comparable across all of them.
Is there an API for JSON formatting?
No, and intentionally so. The whole value proposition is that formatting happens in your browser without an API call. If you need server-side JSON formatting, every programming language has it built in: JSON.stringify(obj, null, 2) in JavaScript, json.dumps(obj, indent=2) in Python, json.MarshalIndent in Go, and so on.
What about formatting JSON Lines (JSONL/NDJSON)?
JSON Lines is a format where each line is a separate JSON document — common in log files and streaming pipelines. Our formatter currently expects a single JSON document. To format JSONL, format each line individually, or convert the file to a single JSON array first. We're considering adding native JSONL support — let us know via the contact page if this would help you.
Does the tool track or log anything?
We use Google Analytics (anonymous pageview data only — never the contents of your JSON) and load Google AdSense for advertising. Neither service has access to your tool inputs. For full details, see our privacy policy.
Large files

Working with a big file? Files over 4 MB stream through a Web Worker instead of being parsed into memory — up to 100 MB. Generate a test file to try it.

Behind the scenes

Everything on this page runs in your browser — no upload, no server-side processing. How it works →

More

Browse all 14 tools — formatting, validation, conversion, patching, canonicalization and type generation, all running in your browser.