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JSON Formatter & Validator

Format, validate, minify and explore JSON — syntax highlighting, tree view, error detection

Features

  • Format & beautify JSON
  • Minify / compress
  • Validate with error line
  • Tree view explorer
  • Sort keys alphabetically
  • Download as .json file
  • Syntax highlighting
  • Live validation

JSON Rules

  • Strings need double quotes
  • No trailing commas
  • No comments allowed
  • Keys must be strings
  • true/false are lowercase
  • null not undefined

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Free JSON Formatter & Validator

The developer's essential tool — instantly format messy JSON into readable, properly indented code, validate syntax with helpful error messages, and explore complex structures with our interactive tree view. Works entirely in your browser with zero data transmission.

Features

Instant Beautify

Transform minified JSON into readable, indented format with one click.

Minify / Compress

Remove all whitespace to minimise JSON for API payloads and storage.

Syntax Validation

Detailed error messages pinpoint exactly where your JSON is invalid.

Tree View Explorer

Navigate nested objects and arrays visually by collapsing/expanding nodes.

Sort Keys

Sort all object keys alphabetically for consistent, diff-friendly output.

Download as .json

Save your formatted JSON directly as a .json file with one click.

Who Uses This Tool?

Backend DevelopersDebug API responses and format configuration files during development.
Data EngineersValidate and inspect JSON data exports from databases and pipelines.
QA EngineersInspect API payloads and webhook bodies during testing.
StudentsLearn JSON structure and syntax with instant visual feedback.

Frequently Asked Questions

What makes JSON invalid?
The most common errors are: trailing commas after the last item, single quotes instead of double quotes, missing quotes on keys, undefined instead of null, and JavaScript-style comments.
What is the difference between beautify and minify?
Beautify adds indentation and line breaks for human readability. Minify removes all whitespace to produce the smallest possible string for machine processing.
Can I format very large JSON files?
Yes — the formatter runs in your browser so there are no server-side size limits. Very large files (50MB+) may be slow depending on your device.
What does "Sort Keys" do?
It recursively sorts all object keys alphabetically at every nesting level. This is useful for version control diffs and standardising API output.

Pro Tip

Use the Tree View to explore deeply nested JSON without losing context. Click the ▼ arrows to collapse sections you've finished reviewing, keeping your focus on the relevant part of the structure.

Did You Know?

2001
JSON Was Born
Douglas Crockford formalized JSON in 2001, though it was derived from JavaScript object notation that had existed since the late 1990s. He called it "the world's most misunderstood programming language."
97%
of Web APIs Use JSON
JSON has overtaken XML as the dominant data format for web APIs. Its human-readable syntax, minimal overhead and native JavaScript support drove this adoption.
RFC 8259
JSON's Official Standard
JSON is standardized by Internet RFC 8259 and ECMA-404. The spec is remarkably short — the entire JSON syntax fits on one page, which is part of its success.

Common JSON Errors

ErrorInvalid ExampleFix
Trailing comma{"a":1,}Remove the last comma
Single quotes{'key':'val'}Use double quotes: {"key":"val"}
Undefined value{"x":undefined}Use null instead
Unquoted key{key:"value"}Quote the key: {"key":"value"}
Comments{"a":1 // comment}Remove all comments — JSON has none
Missing quotes{"n":John}String values need quotes: "John"

More Questions

What is the difference between JSON and XML?
JSON uses key-value pairs with minimal syntax ({} and []). XML uses opening and closing tags like HTML. JSON is typically 30–50% smaller for the same data, much faster to parse, and natively supported in JavaScript. XML supports attributes, namespaces and schemas, making it better for complex document-oriented data.
Can JSON contain comments?
No — standard JSON does not support comments. This is a deliberate design decision by Crockford. If you need comments in config files, use JSONC (JSON with Comments), YAML, or TOML instead. JSON5 is an extended format that allows comments but is not universally supported.
What is the maximum size of a JSON file?
There is no defined maximum in the JSON specification. However, very large JSON files (>50MB) can cause memory issues in browsers. For large datasets, consider streaming JSON parsers (like ndjson or JSON Lines) where each line is a valid JSON object.

Common Mistakes

Using JSON.stringify() for deep comparison
Object key order is not guaranteed in JavaScript, so two identical objects may stringify differently.
Use a deep equality library or sort keys before comparing.
Storing binary data directly in JSON
JSON cannot represent raw binary data. Storing images or files directly causes encoding issues.
Encode binary as Base64 string before placing in JSON.
Assuming JSON preserves number precision
JSON numbers are IEEE 754 floats. Integers larger than 2^53 lose precision. This affects database IDs.
Send large integers as strings in JSON to preserve precision.