JSON Formatter & Validator

Beautify minified JSON, validate syntax, and debug errors instantly. Free online JSON parser that runs 100% in your browser for privacy.

Capabilities

Local Processing
Data never matches server
Large Files
Optimized for 5MB+ text
Privacy First
No logs, no tracking
Standard Compliant
Strict RFC adherence

How It Works

JSON (JavaScript Object Notation) is the language of the web. It's concise, readable, and powerful. But when it's minified or broken, it's a nightmare. This tool is your instant fix for unreadable or invalid JSON.

Why Do We Need a JSON Formatter?

Computers love Minified JSON—JSON with all whitespace removed. It saves bandwidth and loads faster. API responses often look like this:

{"status":"ok","data":[{"id":1,"name":"Alice"},{"id":2,"name":"Bob"}]}

Humans, however, cannot read this efficiently. This tool acts as a "Beautifier" that adds proper indentation (whitespace) and newlines to turn that blob into a structured, readable tree.

⚠️ Common Syntax Errors JSON is stricter than standard JavaScript objects.
  • Keys must be quoted: { name: "Alice" } is valid JS but invalid JSON. It must be { "name": "Alice" }.
  • No Trailing Commas: [1, 2, 3, ] typically crashes a JSON parser.
  • Strict Types: Strings must use double quotes ("). Single quotes (') are forbidden.

Real-World Use Cases

  • API Integration: When connecting to a third-party API (like Stripe, Twilio, or AWS), you will often copy the response body from your terminal or logs. Pasting it here helps you understand the structure immediately.
  • Configuration Files: Many developer tools (VS Code, ESLint, Prettier) use .json config files. A missing comma or mismatched brace effectively breaks your environment.

Technical Deep Dive: BigInt Precision

Standard JSON has a limitation with numbers. It uses 64-bit floating point numbers (IEEE 754). This means very large integers (bigger than 253 - 1) might lose precision.

For example, a Tweet ID like 1500000000000000001 might get rounded to 1500000000000000000. If exact precision is critical for massive integers, ensure you handle them as strings in your application code.

🔒 Security: Why Client-Side Matters Many online formatters send your data to their backend to process it. If you paste a production API key or customer PII, that server could log it.

This tool is different. It runs 100% in your browser using JSON.parse(). Your data never leaves your device.

Frequently Asked Questions

Is my JSON data sent to a server?
No. This tool runs entirely in your web browser using JavaScript. No data is ever sent to our servers, ensuring your API keys and private data remain secure.
Why is my JSON invalid?
Common reasons include missing quotes around keys, trailing commas (which are not allowed in standard JSON), or using single quotes instead of double quotes.
Can I format large files?
Yes. Since we process data locally, we can handle significantly larger files than server-based tools without timing out, limited only by your browser's memory.

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