Developer Utility
Free JSON Formatter & Validator 2026
Format, validate, and minify JSON instantly. Catch syntax errors, sort keys, compare sizes, and copy your result with one click. Free, no signup.
Instant Formatting
Syntax Validation
Minify JSON
Sort Keys
JSON Formatter & Validator
Paste JSON → choose options → Format & Validate
How to Use the JSON Formatter
3 quick steps to format or validate any JSON
1
Paste Your JSON
Paste any raw, minified, or partially malformed JSON into the input box. Use "Load Sample" to try an example first.
2
Set Options
Choose your indent size (2 or 4 spaces is most common) and optionally enable Sort Keys to alphabetise all object properties.
3
Format & Copy
Click the button — formatted and minified outputs appear with size stats. Switch tabs and copy with one click.
What Is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data-interchange format. It represents data as key-value pairs, arrays, strings, numbers, booleans, and null — universally readable by humans and machines.
Standardised as RFC 8259, JSON is the dominant format for REST APIs, configuration files, NoSQL databases (MongoDB, CouchDB), browser localStorage, and inter-service communication in microservice architectures.
Format vs Minify vs Validate
Format / Prettify — adds indentation and newlines for readable, diff-friendly JSON
Minify / Compress — strips all whitespace to reduce file size in production APIs
Validate / Lint — checks syntax and reports the exact line and column of any parse error
Sort Keys — alphabetises all keys for consistent diffs and deterministic output
JSON Data Types Reference
All valid JSON value types with syntax examples
| Type | Example Value | Notes |
|---|---|---|
| String | "Hello, World!" | Must use double quotes — single quotes are invalid JSON |
| Number | 42, 3.14, -7, 1e10 | Integer or float; no quotes; NaN and Infinity are not valid |
| Object | {"key": "value"} | Keys must be strings in double quotes; values any JSON type |
| Array | [1, "two", true] | Ordered list; can mix any JSON types; no trailing commas |
| Boolean | true, false | Lowercase only — True/False (Python casing) are invalid |
| Null | null | Represents absence of value; lowercase only |
Common JSON Errors & Fixes
The most frequent JSON syntax mistakes and how to correct them
Trailing Comma
{"name":"Ali",}Remove the comma after the last item. JSON does not allow trailing commas in objects or arrays.
Single Quotes
{'name': 'Ali'}Replace single quotes with double quotes. JSON requires double quotes for both keys and string values.
Unquoted Keys
{name: "Ali"}All object keys must be wrapped in double quotes. Unquoted keys are JavaScript syntax, not JSON.
Comments in JSON
{"x": 1 // comment}JSON does not support comments. Remove all // or /* */ comments before parsing.
Python Casing
{"active": True, "val": None}JSON requires lowercase:
true, false, null. Python capitalisation is not valid. NaN / Infinity
{"value": NaN}JSON does not support NaN, Infinity, or undefined. Replace with null or a fallback value.
Frequently Asked Questions
Common questions about JSON formatting and this tool
What is the difference between JSON and JavaScript objects?
JSON is a strict text format derived from JavaScript object literal syntax, but they differ: JSON requires double quotes on all keys, does not allow comments or trailing commas, and does not support special values like undefined, NaN, or functions. A JavaScript object can use all of these freely.
What indent size should I use — 2 or 4 spaces?
Both are valid. 2 spaces is the most common choice in JavaScript/Node.js projects and Google's style guide. 4 spaces is preferred in Python (PEP 8) and many Java projects. The choice is purely cosmetic — both produce identical, valid JSON.
What does "Sort Keys" do exactly?
Sort Keys alphabetises all keys at every level of nesting. This produces deterministic output — the same input always produces the same output regardless of original key order. Useful for version control diffs, caching, and comparing two JSON objects for equality.
How much does JSON minification reduce file size?
JSON minification typically reduces size by 15–30% for typical API payloads. The stat shown in results is the exact percentage for your specific input. Combined with gzip compression (applied automatically by most web servers) you can achieve 70–90% total reduction.
Can this tool fix invalid JSON automatically?
No. This tool validates and reports errors but does not auto-repair broken JSON. Auto-repair risks silently producing incorrect data. The error message shows the exact line and character position of the fault so you can fix it manually.
Is my JSON data stored or logged by AZRS?
AZRS Corp does not permanently store or share your JSON input. The history feature stores only metadata (validity flag and timestamp) for logged-in users — not the JSON content itself.
Why Use AZRS JSON Formatter?
Instant Server-Side Formatting
No JavaScript lag — processed server-side for reliability on large files.
Format & Minify in One Click
Both outputs appear simultaneously — switch between tabs instantly.
Size Reduction Stats
See exactly how many characters minification saves — useful for API optimisation.
Validation History
Track your recent validations without needing to re-run them manually.