Format messy JSON, validate syntax, and beautify output instantly—perfect for developers and APIs.
Format JSON online instantly with this fast, free JSON formatter and validator. Ideal for developers working with APIs, config files, and debugging workflows.
Validate, minify, or beautify JSON in seconds. This JSON formatter works as a JSON beautifier for messy payloads, and it runs entirely in your browser for maximum speed and privacy—no upload required.
Used by developers to format and debug JSON data quickly and efficiently.
By EverydayTools Team ·
Tip: Paste your JSON and click Format to beautify it, or Validate to check for errors. Use Minify to compress JSON for production use.
⭐ Bookmark this page to quickly format JSON anytime.
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JSON (JavaScript Object Notation) is a lightweight, text-based data format used for storing and exchanging structured data. Originally derived from JavaScript, it is now language-independent and supported by virtually every programming language — from Python and Java to PHP, Go, and Rust. The format is defined by RFC 8259 and is the dominant data format for REST APIs, configuration files, and web services worldwide.
JSON represents data as key-value pairs inside curly braces {}, and ordered lists inside square brackets []. It supports six data types: strings, numbers, booleans (true/false), null, objects, and arrays. Its simplicity is why it replaced XML as the dominant data-interchange format on the web.
A JSON formatter is a tool that takes raw, minified, or badly indented JSON and renders it with consistent indentation and line breaks, making it easy for humans to read. It is also called a JSON beautifier or JSON pretty-printer. Beyond aesthetics, a good JSON formatter also validates syntax — it tells you exactly where an error is (line and column number) when your JSON is malformed.
This tool formats JSON entirely in your browser. Nothing is uploaded to a server, which matters when the JSON contains API keys, authentication tokens, or personal data. It also means it works instantly, with no round-trip network delay.
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Below is an example of messy JSON converted into a clean, readable format using this JSON formatter:
{"name":"John","age":30,"city":"NY"}{
"name": "John",
"age": 30,
"city": "NY"
}Try formatting your own JSON above to see the difference instantly.
When you use fetch(), Postman, or curl to call an API, the response is often a single minified line. Pasting it into this formatter instantly expands it into a readable structure so you can identify which field contains unexpected data or which key is missing.
Tools like package.json, tsconfig.json, eslintrc.json, and VS Code settings.json are all JSON. When a config gets messy or throws a parse error, this formatter validates it and pinpoints the exact broken line.
A JWT payload is Base64-encoded JSON. After decoding it (use our JWT Decoder), you can paste the payload here to read and validate the claims structure cleanly.
Stripe, GitHub, Shopify, and most modern SaaS platforms send webhook data as JSON. When troubleshooting a missed event or an unexpected field, paste the raw webhook body here to see the exact structure in seconds.
When migrating data between systems, JSON files often arrive malformed or with inconsistent indentation. This formatter validates and normalizes the structure before you feed it into a database import or transformation script.
When writing tests or adding fixture data, properly formatted JSON is much easier for reviewers to understand. Run it through this formatter before committing so diffs are clean and readable.
JSON has strict syntax rules. These are the most common causes of invalid JSON:
| Rule | Valid | Invalid |
|---|---|---|
| Keys must be strings | "name": "John" | name: "John" |
| No trailing commas | [1, 2, 3] | [1, 2, 3,] |
| No comments | {"key": "val"} | {"key": "val"} // comment |
| Use double quotes | "name": "Alice" | 'name': 'Alice' |
| Boolean lowercase | {"active": true} | {"active": True} |
JSON is the dominant format for APIs and web services, but it is worth understanding when XML and YAML are preferable:
| Format | Best For | Drawback |
|---|---|---|
| JSON | REST APIs, web apps, config files | No comments, no schema by default |
| XML | SOAP services, document formats, namespaces | Verbose, harder to read and parse |
| YAML | CI/CD configs (GitHub Actions, Docker Compose) | Indentation-sensitive, easy to break |
JSON.parse() — use try/catch or a validator first.Explore more tools to validate, compare, and work with JSON data efficiently.
Before formatting transformed text payloads, validate the replacement logic in Regex Tester.
JSON.parse().Use the tool above to format, validate, or minify JSON instantly.
Concise answers for common searches — definitions, steps, and comparisons.
JSON supports exactly six value types: string (double-quoted), number (integer or decimal, no quotes), boolean (true or false, lowercase), null, object ({key: value} pairs), and array ([value, value]). JSON does not support: undefined, functions, Symbol, NaN, Infinity, single-quoted strings, or comments. A key that maps to undefined is silently dropped by JSON.stringify() — use null instead.
Inside a JSON string, these characters must be escaped with a backslash: " (double quote → \"), \ (backslash → \\), and control characters (newline → \n, tab → \t, carriage return → \r, form feed → \f, backspace → \b). Unicode escapes use \uXXXX notation. Unescaped control characters cause a SyntaxError.
Minification removes all whitespace between tokens: JSON.stringify(JSON.parse(input)) returns compact JSON with no spaces or line breaks. A typical well-indented JSON object compresses 15–30% by minification. For a REST API that transfers hundreds of KB per request, minification reduces bandwidth and speeds parsing. The data is structurally identical — only whitespace is removed.
Copy raw JSON from an API response, log output, or config file and paste it. The formatter accepts minified single-line JSON, partially indented JSON, and will flag broken JSON.
Select 2 spaces (JavaScript/TypeScript convention) or 4 spaces (Python/Java convention). Both produce valid, equivalent JSON — choose based on your project's style guide.
If your JSON is invalid, the error message shows the exact line and column of the syntax problem. Fix errors before copying to avoid downstream parsing failures.
Click 'Copy' to grab formatted JSON, 'Download' to save as a .json file, or 'Minify' to compress the output back to a single line for production payloads.
Common real-world scenarios where this tool saves time.
Paste raw minified API output to instantly see the nested structure and identify missing or unexpected fields. Works with any REST or GraphQL response body.
Validate package.json, tsconfig.json, .eslintrc, manifest.json, or any JSON config before committing — catches trailing commas, missing brackets, and unquoted keys before CI fails.
Stripe, GitHub, and Shopify webhooks arrive as minified JSON. Format them to trace missed events, verify payload structure, and identify which fields triggered your handler logic.
Normalize inconsistent JSON from external data sources before feeding into an ETL pipeline, database import, or transformation script — catches malformed records before they reach production.
Step-by-step chains that connect related tools for common tasks.
When a REST API response looks broken, confirm syntax before prettifying — formatting invalid JSON does not fix parse errors and can hide the failure point.
Input
{"status":"ok","user":{"id":42,"email":"alice@example.com","roles":["admin","editor"]},"created_at":1746172800}Output
{
"status": "ok",
"user": {
"id": 42,
"email": "alice@example.com",
"roles": [
"admin",
"editor"
]
},
"created_at": 1746172800
}The formatted output reveals the nesting depth — user is an object containing id, email, and a roles array. The raw minified version requires scanning for brackets to understand the same structure. Formatting is the first debugging step when an API returns unexpected data.
Input
{"name": "alice", "active": true, "score": 98,}Output
SyntaxError: Unexpected token } — line 1, column 46Trailing commas after the last property are valid JavaScript but invalid JSON. This is the most common cause of JSON.parse() failures when copy-pasting object literals from JS code into API request bodies or config files.
The formatter passes input to the browser's native JSON.parse(), which throws a SyntaxError with the byte offset of the first invalid character. On success, JSON.stringify(parsed, null, indentSize) re-serializes the structure with configurable indentation. Minification calls JSON.stringify(parsed) with no indent argument. Both operations run entirely in the JavaScript main thread and are O(n) in input length.
Formula
Format: JSON.stringify(JSON.parse(input), null, indentSpaces)
Minify: JSON.stringify(JSON.parse(input))
Error: SyntaxError at byte N → converted to line:columnEach format has strengths suited to specific ecosystems. JSON is the default for APIs; YAML dominates in DevOps tooling; XML is mostly legacy.
| Format | Syntax style | Best for | Not ideal for |
|---|---|---|---|
| JSON | Braces, brackets, double-quoted keys | REST APIs, config files, JavaScript data exchange | Human-edited files that benefit from comments |
| YAML | Indentation-based, minimal punctuation | DevOps configs (Kubernetes, GitHub Actions, Ansible) | Machine-to-machine exchange; whitespace bugs are common |
| XML | Verbose open/close tags with attributes | Enterprise systems, SOAP APIs, SVG, XSLT pipelines | Readability, file size, simplicity |
| JSONC | JSON + // and /* */ comments | VS Code settings.json, developer tool configs | Standard JSON parsers; technically not valid JSON |
| JSON5 | Relaxed: unquoted keys, trailing commas, comments | Human-maintained config files | Strict RFC 8259 compliance requirements |
JSON is the default for programmatic data exchange. YAML is dominant in DevOps tooling. XML is mostly legacy except in enterprise and document-centric contexts.
| Related tool | Use this tool when | Use related tool when |
|---|---|---|
| JSON Validator | You want to format readable output and validate in one step, or need to minify the output. | You only need a pass/fail validity check with the precise error location, without reformatting the output. |
| YAML Formatter | Your data is in JSON format — API responses, config files, package.json. | Your config is in YAML format — GitHub Actions, Kubernetes, Docker Compose, Ansible. |
| JSON Diff Viewer | You have one JSON payload to inspect, validate, and clean up. | You have two JSON objects and need to identify exactly what changed between them. |
| JWT Decoder | You have a raw JSON API response to format and explore — including any string fields that happen to be tokens. | You have identified a JWT token string inside the JSON payload (the value of an 'access_token', 'token', or 'authorization' field) and need to decode its header and claims. |
| Timestamp Converter | You need to format the full JSON response and see which fields contain Unix timestamps. | You have identified a numeric Unix timestamp field (created_at, updated_at, iat, exp) in the formatted JSON and want to convert it to a readable date. |
Minified JSON forces you to count brackets to find nesting depth. Formatting takes one second and eliminates most of the cognitive overhead when a field is missing or the structure is deeper than expected.
Prettier, ESLint, and npm defaults all use 2-space indent. Consistent indentation reduces diff noise in code reviews and aligns config files with the rest of the codebase.
A 100 KB config with 2-space indent is approximately 70 KB minified — a 30% reduction. Minified JSON parses marginally faster and reduces network transfer in API responses.
Trailing commas, missing brackets, and JSONC comment syntax are the top causes of CI build failures in package.json, tsconfig.json, and manifest.json. A 3-second validation prevents a 3-minute CI queue wait.
JSON requires double quotes for all keys and string values. {name: 'alice'} is valid JavaScript but invalid JSON. Use double quotes: {"name": "alice"}. The formatter shows the exact character position of the error.
[1, 2, 3,] and {"a": 1,} are invalid JSON, though they are valid JavaScript. Remove the comma after the final item. This is the most common source of JSON.parse() errors when copying from JS files.
JSON does not support // or /* */ comments. They work in JavaScript and TypeScript's tsconfig.json (which uses JSONC format), but not in files parsed by JSON.parse(). Move comments to external documentation or use a JSONC parser.
JSON.stringify() silently drops object properties set to undefined and converts undefined array items to null. The result looks like the property never existed. Use null for intentionally absent values: { "result": null }.
Windows Notepad and some export tools prepend a UTF-8 BOM (\uFEFF) when saving. The character is invisible in most editors but causes JSON.parse() to throw 'Unexpected token' in Node.js and strict server parsers. Always save JSON files as UTF-8 without BOM.
Likely cause: BOM character (\uFEFF) at the start of the string — common in JSON files saved by Windows Notepad
Fix: Strip the BOM before parsing: input.replace(/^\uFEFF/, ''). The browser JavaScript engine accepts BOM-prefixed input silently; Node.js and strict server parsers do not.
Likely cause: IEEE 754 double-precision cannot represent integers above 2^53 − 1 exactly. Snowflake IDs and database bigint values above 9,007,199,254,740,991 are silently rounded.
Fix: Store large IDs and 64-bit timestamps as strings in JSON: { "id": "9007199254740993" }. The Twitter and Discord APIs both use this pattern for their ID fields.
Likely cause: JSON body is double-encoded (a string containing JSON), Content-Type header is missing, or a BOM was introduced during copy-paste
Fix: Verify Content-Type: application/json is set. Confirm the raw body is the JSON string directly, not URL-encoded or wrapped in another layer of quotes.
Likely cause: V8 sorts integer-like string keys numerically before other string keys — a non-obvious engine behavior
Fix: JSON key order is not guaranteed by the ECMA-404 spec. If your API or snapshot test depends on key order, sort keys explicitly in the producing code rather than relying on JSON.stringify output order.
Likely cause: undefined, functions, and Symbol values are silently stripped by JSON.stringify — they have no JSON representation
Fix: Replace undefined with null before serializing. JSON.stringify({ a: undefined }) returns {} — the key disappears entirely. Use null for intentionally absent values: { "a": null }.
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No. All formatting and validation runs locally in JavaScript inside your browser. Your data never leaves your device — safe for API keys, tokens, database credentials, internal service configs, and any sensitive data.
Trailing commas after the last element, unmatched braces and brackets, single-quoted strings, unquoted keys, missing commas between items, invalid Unicode escape sequences (\uXXXX), and invalid number formats. Each error reports the exact line and column number.
JavaScript objects allow unquoted keys ({name: 'alice'}), single-quoted strings, trailing commas, and comments. JSON requires double-quoted keys ({"name": "alice"}), no trailing commas, and no comments. All valid JSON is valid JavaScript, but not vice versa — this mismatch is the source of most copy-paste errors.
Yes. Processing runs locally so there is no upload size limit or server timeout. Most JSON under 10 MB formats instantly. Files above 50 MB may take a few seconds depending on your device.
Formatting adds indentation and line breaks for human readability. Minifying removes all whitespace to reduce file size — typically 15–30% smaller — for production API payloads and bundle assets. This tool handles both: format for debugging, minify for deployment.
Yes — completely free, no signup required, no usage limits. It runs entirely in your browser.
All formatting, validation, and minification runs in your browser using the JavaScript engine. No data is ever sent to any server — safe for API keys, tokens, database credentials, and any sensitive payload.
Formatted output is semantically identical to input. The tool uses the same JSON.parse / JSON.stringify pipeline as Node.js and all major browsers. There is no custom parser or transformation.
Formatted output is for human readability only. Validate JSON before using in production systems.
Part of Developer Tools
More free tools for the same workflow.
Free JSON diff tool — compare two JSON objects side by side and instantly highlight added, removed, and changed keys. Ideal for debugging API responses and config changes.
Free JSON path finder — click any value in a formatted JSON tree to instantly copy its JSONPath expression. Ideal for navigating deep API payloads and config files. No signup.
Free JSON Schema generator — paste sample JSON and instantly generate a JSON Schema Draft-7 with inferred types, required fields, and nested object definitions. No signup.
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Reviewed by EverydayTools Editorial Team on 2026-05-14.