JSON Formatter & Validator

What is JSON Formatter?

A JSON formatter (also called a JSON beautifier or pretty-printer) takes minified or messy JSON and reformats it with consistent indentation, sorted keys, and syntax highlighting. It's one of the most used tools in a developer's daily workflow — for reading API responses, debugging config files, and validating structure before sending payloads.

How to format JSON online

1. 1Paste your raw JSON into the left editor, or drop a .json file onto the page.
2. 2The right pane instantly renders indented, syntax-highlighted output.
3. 3If the JSON is invalid, the error location (line and column) is shown at the top of the input pane.
4. 4Click the Copy button to grab the formatted result, or Download to save it as a .json file.

Use Cases

Code Examples

const formatted = JSON.stringify(obj, null, 2);
console.log(formatted);

import json
print(json.dumps(obj, indent=2, sort_keys=True))

echo '{"a":1,"b":2}' | jq .

import "encoding/json"

out, _ := json.MarshalIndent(obj, "", "  ")
fmt.Println(string(out))

Key Concepts

JSON (RFC 8259)

A lightweight, language-independent data-interchange format. Only 6 structural characters, 3 literals, and strings/numbers — that's the entire grammar.

JSON Schema

A vocabulary for validating JSON documents against a declared shape. Different from formatting — schema tells you if data is correct, formatter makes it readable.

JSONC

JSON with comments, popularized by VS Code config files. Not standard JSON — strip comments before feeding into a strict parser.

JSON5

A superset of JSON allowing comments, trailing commas, and unquoted keys. Useful for hand-written configs but not accepted by standard JSON parsers.

Tips & Best Practices

• ▸Use 2-space indent for API payloads, 4-space for config files — both are widely supported conventions.
• ▸If your JSON contains 100k+ keys, consider streaming parsers (like `stream-json` in Node or `ijson` in Python) instead of loading the whole document.
• ▸Never trust `eval()` to parse JSON. Always use `JSON.parse()` or a dedicated library — eval is a code-execution vulnerability.
• ▸For diffs in code review, sort keys before committing — makes reviews much cleaner. Both this tool and `jq -S` do this.