JSON Formatter & Validator
Format, validate, and beautify JSON entirely in your browser.
JSON is parsed and formatted in-browser using JSON.parse and JSON.stringify, so no data is sent to a server at any point. Syntax errors are caught and surfaced immediately so you can fix them without leaving the page.
JSON Formatter & Validator
Pretty-print, minify, and validate JSON entirely in your browser.
Compare Two JSON Values
Paste two JSON values to see what was added, removed, or changed between them. Compared locally; nothing is sent anywhere.
Paste any JSON to validate its syntax, pretty-print it with consistent indentation, or minify it down to a single line. Parsing happens entirely client-side: invalid JSON reports the line and column of the error so you can find the problem quickly.
Why Client-Side JSON Formatting Is Different
Many online JSON formatters work by posting your input to a server, formatting it there, and returning the result. That round trip means anything you paste in (API responses, configuration files, sample payloads that may contain tokens or internal hostnames) passes through a third party's infrastructure and potentially its logs.
This formatter runs entirely in your browser using the built-in JSON.parse() and JSON.stringify()functions. Parsing and re-serialising happen in the same JavaScript engine that renders the page. There is no network request involved in the formatting step itself, so there's nothing for a server to see or log.
Validation vs. formattingare related but distinct: a payload can be syntactically valid JSON (correctly balanced braces, quoted keys, no trailing commas) while still failing to match the schema an application expects. This tool checks syntax: it will catch a missing comma or an unescaped quote, but it doesn't know whether a field should be a number versus a string in your specific application. For that level of validation you'd need a JSON Schema validator configured for your data shape.
The syntax errors this tool catches tend to fall into a small set of repeat offenders: a trailing comma after the last item in an array or object (valid in JavaScript object literals, invalid in strict JSON), unquoted or single-quoted keys, a missing closing brace after a deeply nested structure, or a stray comment, since JSON has no comment syntax at all, unlike JSON5 or JSONC, so a // or /* */ left over from a JavaScript file will fail to parse every time. Knowing which of these produced a given error is often faster than reading the raw parser message, which typically just reports a line and column number rather than naming the actual mistake.
JSON's appeal as a data format is precisely that it's this constrained: a small, unambiguous grammar with no comments, no trailing commas, and exactly one way to represent a string, number, boolean, null, array, or object. That rigidity is what makes it parseable identically across every language and platform. The tradeoff is that a single missing quote or comma fails the entire document rather than degrading gracefully, which is exactly the class of problem a fast, local formatter is built to surface immediately.
Common Use Cases
Pretty-printing a minified API response
Copying a minified JSON response straight from a network tab and formatting it here makes it readable before you go digging through it for the field you actually need.
Reading a single-line log dump
Structured logs often get emitted as a single JSON line. Formatting one before reading it turns a wall of text into something you can actually scan for the field that matters.
Cleaning up a pasted config file
A config file someone pastes into a chat or ticket without its original line breaks is hard to review as-is. Formatting it restores the structure so you can actually check the values.
Catching a syntax error before it reaches your app
Pasting a hand-edited JSON file here before committing it catches a trailing comma or an unquoted key immediately, instead of finding out from a parse error at runtime.
Frequently Asked Questions
Is my JSON data sent to a server for formatting?
No. All formatting and validation happens locally in your browser using the native JSON.parse() and JSON.stringify() APIs. Your data never leaves your device.
What does the formatter validate?
It checks that the input is syntactically valid JSON. If parsing fails, it reports the error. It does not enforce schema compliance: it validates structure, not semantics.
What is the maximum input size?
The formatter accepts inputs up to 1,000,000 characters. Very large payloads may briefly pause the UI while parsing.
What indentation level should I use?
2 spaces is the most common convention for JSON stored in source control or configuration files. 4 spaces is common in some ecosystems. The choice is stylistic and has no effect on how the JSON is parsed.
Further Reading
How to Fix "Unexpected Token" JSON Parse Errors
A walkthrough of the most common "Unexpected token" JSON parse errors, what each one actually means, and how to fix them quickly.
JSON Schema Validation: Syntax Errors vs Schema Errors
The difference between JSON that fails to parse and JSON that parses fine but violates a schema, and why tooling should treat them separately.
Why Your JSON.stringify() Output Looks Different From What You Expected
Why JSON.stringify() silently drops fields, reorders keys, or throws on circular references, and what to do about each case.