🔷 JSON Formatter & Validator

Real-time JSON formatting, validation, and syntax highlighting.

Waiting for input…
INPUT JSON
FORMATTED OUTPUT
Formatted output will appear here

About this JSON Formatter & Validator

JSON (JavaScript Object Notation) is the universal data format for REST APIs, configuration files, and inter-service communication. But raw JSON returned by APIs is usually a single minified line, making it nearly impossible to read or debug. This free online JSON formatter instantly pretty-prints any valid JSON with proper indentation, colour-coded syntax highlighting, and tree-view navigation — right in your browser, with zero data sent to any server.

Beyond formatting, the tool acts as a live JSON validator. As you type or paste, it continuously parses your input and pinpoints the exact line and character of any syntax error — stray commas, missing quotes, mismatched brackets. Developers working with Spring Boot, Node.js, Databricks, or any REST API will find this indispensable for daily debugging.

How to use the JSON Formatter

  1. Paste your JSON into the left panel. The formatter validates it instantly and shows a green ✓ Valid badge or a red ✗ Invalid badge with the error location.
  2. Choose indentation — 2 spaces (default), 4 spaces, or Tab — from the dropdown in the output panel header.
  3. Toggle Sort Keys to alphabetically sort all object keys. Useful for comparing two API responses side-by-side.
  4. Toggle Highlight to switch between colour-coded syntax view and plain monochrome text.
  5. Switch to Tree view (🌳 Tree button) to navigate deeply nested objects with click-to-expand nodes.
  6. Minify with the top button to strip all whitespace for production payloads or clipboard use.
  7. Copy the formatted output with one click using the ⎘ Copy button.

Features

🔷 Real-time formatting

JSON is formatted as you type with zero delay. No button click needed — just paste and read.

🔒 100% Private

All formatting runs locally in your browser using JavaScript. Nothing is ever sent to a server or stored.

✅ Instant validation

Shows if your JSON is valid with exact line and character position of any syntax error.

🗜 Minify

Remove all whitespace and line breaks to create compact JSON for API payloads or storage.

🔤 Sort Keys

Alphabetically sort all object keys at every nesting level — great for diff comparisons.

🌳 Tree view

Navigate deeply nested structures with a collapsible tree. Click any node to expand or collapse it.

Frequently Asked Questions

Why is my JSON showing as invalid when it looks correct?

The most common culprits are: a trailing comma after the last item in an object or array (not allowed in standard JSON), single quotes instead of double quotes around keys or string values, or an unescaped special character like a newline inside a string. The error message will tell you the exact line and column — look one token before that position for the actual mistake.

What is the difference between JSON formatting and JSON minifying?

Formatting (pretty-printing) adds consistent indentation and line breaks to make JSON readable. Minifying strips all unnecessary whitespace to produce the smallest possible representation. Use formatted JSON for development and debugging, and minified JSON for production API payloads or storage where byte size matters.

Does this tool support very large JSON files?

Everything runs in your browser, so there is no upload and no size limit imposed by a server — the practical ceiling is your own machine. Documents up to a few hundred KB are comfortable; past roughly a megabyte, syntax highlighting and folding start to cost more than they are worth. For files in the hundreds of megabytes, a streaming command-line tool like jq (jq . file.json) is the right instrument, because it never has to hold the whole document in memory.

What does 'Sort Keys' do and when should I use it?

Sort Keys alphabetically reorders all object keys at every nesting level. This is useful when comparing two JSON objects that represent the same data but have keys in different orders, or when you want a canonical representation for checksumming.

Can I use keyboard shortcuts?

Yes — press Ctrl+Enter (or Cmd+Enter on Mac) to re-format the current input. This is handy after making edits directly in the input pane.

Is this JSON formatter safe to use with sensitive data?

All processing happens entirely in your browser using JavaScript — no data is transmitted to any server. However, be cautious when using any web tool on shared or public computers. For highly sensitive production secrets or personal data, running a local tool like jq is always the safer choice.

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Developer guide

Complete guide to JSON formatting and validation

JSON (JavaScript Object Notation) is the standard data exchange format for REST APIs, webhooks, configuration files, and microservice communication. When JSON arrives from a network call, a browser console, or a log file, it is usually compressed onto a single line to reduce payload size. That makes it nearly unreadable when you need to inspect it quickly during development or an incident.

Braxik's JSON formatter takes any valid JSON string and rewrites it with consistent indentation, aligned braces, and line breaks between every key-value pair. The result is the same data structure, but structured in a way that lets you scan nested arrays and objects without losing your place.

Before formatting, the tool validates the input against the JSON specification. If your input contains a syntax error — a missing comma, a trailing comma after the last property, a single-quoted string, or an unquoted key — the formatter reports the exact line and column so you can fix it without guessing.

You can also use the minify mode to do the reverse: collapse a formatted block back to a single line. This is useful when you want to paste a JSON value into an environment variable, a curl request body, or a command-line argument where newlines would cause errors.

How it works

The formatter parses your input using the browser's built-in JSON.parse() function, which implements the full JSON specification. If parsing succeeds, the resulting object is serialised back to text using JSON.stringify() with a configurable indent level. This two-step process guarantees that the output is always valid and structurally identical to the input.

Key sorting applies a recursive alphabetical sort to every object in the tree before serialisation. This is useful when you want to compare two payloads visually, because consistent key ordering removes the noise of arbitrary insertion order.

Minification works the same way but passes zero indentation to JSON.stringify(), so all whitespace between tokens is removed. The result is the most compact valid JSON representation of your data.

Common uses

  • Debug REST API responses from Spring Boot, Node.js, or Django before sharing them in tickets or pull requests.
  • Verify whether a copied browser payload, Postman body, or webhook event is syntactically valid JSON before sending it to another service.
  • Minify a large JSON configuration before storing it in a Kubernetes secret, environment variable, or feature flag system.
  • Expand a compressed log line from an ELK stack or CloudWatch to find which field caused an error.
  • Sort keys alphabetically before diffing two similar configurations side by side.
  • Clean up generated JSON from code-generation tools or serialisation libraries that produce inconsistent spacing.
  • Inspect deeply nested GraphQL responses to confirm that the expected fields are present and correctly typed.

Before you rely on the result

  • Keep all string values inside double quotes; single quotes and backticks are not valid JSON and will cause a parse error.
  • Remove trailing commas after the final property in an object or after the last element in an array.
  • Make sure all keys are also quoted as strings — JavaScript shorthand property names and bare identifiers are not valid JSON.
  • Use the sort keys option only when key order does not matter for your review; some APIs treat key order as meaningful.
  • Never paste production secrets, API keys, or personally identifiable information into any browser-based tool unless you are certain it runs fully offline.
  • After formatting, check that the structure depth matches your expectations — an extra wrapping array or object is a common source of downstream parsing errors.
  • When debugging Spring Boot or Jackson errors, check that Java null fields are serialised as JSON null rather than omitted, depending on your NullValueHandling configuration.