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{ JSON formatter }

Format, beautify and validate JSON with configurable indentation. Find syntax errors by exact position and copy clean JSON: processed in your browser, kept on your device.

format_indent_increaseBeautifyruleValidatecompressMinify

indent

2 spaces4 spacesTab

data_objectSamplebug_reportBroken sample

format_indent_increaseFormatcompressMinifycontent_copyCopyClear

input.json1 lines · 256 B

formatted.json31 lines · 428 B · 167% of input

2 "user": {

3 "id": 4821,

4 "name": "Ada Lovelace",

5 "roles": [

6 "admin",

7 "editor"

8 ],

9 "active": true,

10 "lastLogin": null

11 },

12 "settings": {

13 "theme": "dark",

14 "notifications": {

15 "email": true,

16 "push": false

17 }

18 },

19 "items": [

20 {

21 "sku": "FF-01",

22 "qty": 2,

23 "price": 19.99

24 },

25 {

26 "sku": "FF-02",

27 "qty": 1,

28 "price": 4.5

29 }

30 ]

31}

errorInvalid JSON

line 0column 0position 0

lightbulb

data_objectformatted output appears here

valid JSON · 18 keys · depth 3shield_lockprocessed locally · nothing sent

~/use-cases

When you'll reach for it.

From a raw API response to a config file that's about to go to production.

apidebug

Debug API responses

Paste a raw response to see its structure instantly. Malformed data from external APIs is flagged right away.

rocket_launchvalidate

Validate before deployment

Invalid JSON in config files causes silent failures. Check syntax before it reaches production.

compressminify

Minify for production

Strip whitespace to shrink API payloads and stored config: typically 30-50% smaller, no data lost.

comparecompare

Compare structures

Format two objects separately; indentation makes nested keys and array depth obvious side by side.

settingsconfig

Check configuration files

One missing comma can break a config. A quick validation catches it before it crashes anything.

schoollearn

Learn JSON structure

Indentation levels show exactly how deep nesting goes and which keys belong to which object.

lockprivate

Safe for sensitive data

Formatting runs locally in your browser. Tokens, payloads and internal data stay on your device.

databasestore

Prepare for storage or transfer

Format first to verify validity, then minify before saving to a database or sending over the network.

~/format-vs-minify

Formatting vs minification.

Same data, different purpose. Format first to verify it's valid, then minify for production.

Aspect

format_indent_increaseFormatted

compressMinified

Whitespace

Indented, with line breaks between elements

All non-essential whitespace removed

File size

Larger: typically 2-3× bigger

Smallest possible size, saves bandwidth

Readability

Highly readable, shows structure clearly

Difficult for humans to read

Use case

Debugging, documentation, code review, learning

Production APIs, stored data, config files

Processing speed

Parses as fast as minified

Slightly faster network transfer

Data integrity

Values unchanged: only whitespace added

Values unchanged: only whitespace removed

~/fix-errors

How to validate and fix JSON errors.

content_paste01

Paste and read the status

Paste your JSON. The tool shows success or an error immediately: errors include the exact character position.

Unexpected token } in JSON at position 245

my_location02

Jump to the position

Use Go to Line (usually Ctrl+G) in your editor. Look for missing commas, unescaped quotes, trailing commas, mismatched brackets or single-quoted keys.

line 3 · column 34

task_alt03

Fix and retest

Paste the corrected JSON back in. Once it validates, Format to check the structure with proper indentation.

✓ valid JSON

Common problems

Error: “Unexpected token ' in JSON”{'name':'John'}{"name":"John"}

buildJSON requires double quotes around every key and string value: single quotes aren’t valid. Search for single quotes and replace them. This is the most common JSON error.

Error: “Unexpected token undefined”[1,2,3,][1,2,3]

buildUsually a trailing comma after the last item in an array or object. Remove the comma before the closing bracket or brace.

Success, but the output is empty

buildYou probably pasted an empty string or only whitespace. There’s nothing to format: paste your actual JSON and try again.

Large files format slowly or freeze the browser

buildFiles over about 50 MB can overwhelm browser memory. Split the JSON into smaller chunks, or use a desktop editor built for large data.

~/valid-but-different

Valid JSON that two programs read differently.

RFC 8259 leaves several things to the implementation: how big a number can be, what happens to a repeated key, whether a broken Unicode escape is allowed. A payload can pass every validator and still mean different things in JavaScript, Python and Go. The JavaScript column below is computed live by this browser’s own JSON.parse.

Large integersprecisionDuplicate keysambiguousLone surrogateunicodeNegative zeronumbersHuge exponentnumbersByte order markencodingA bare stringtop levelNaNnot JSON

input, exactly as received{"id": 9007199254740993}UTF-8: 7B 22 69 64 22 3A 20 39 30 30 37 31 39 39 …

what the standard saysNumbers have no size limit in the grammar. RFC 8259 warns that values outside ±(2^53 − 1) may not be exact, because many parsers use IEEE 754 doubles.

parserreads it aswrites it back as

JavaScriptJSON.parse · this browser{"id":9007199254740992}{"id":9007199254740992}

Python 3json.loads9007199254740993 (int){"id": 9007199254740993}

Goencoding/json → any9007199254740992 (float64){"id":9007199254740992}

shieldSend IDs and money as strings, or parse with BigInt-aware readers. Twitter’s API added id_str for exactly this reason.

~/escapes

Which characters a JSON string has to escape.

Only three kinds are mandatory: the double quote, the backslash and the 32 control characters below U+0020. Everything else, including emoji, may appear as it is in UTF-8. Some encoders escape all non-ASCII anyway (Python’s default ensure_ascii=True), and characters beyond U+FFFF then become a pair of \u escapes. Type anything to see it encoded.

string value

Raw UTF-8ASCII only (\u)

T-U+0054a-U+0061b-U+0062␉\tU+0009h-U+0068e-U+0065r-U+0072e-U+0065␣-U+0020"\"U+0022q-U+0071u-U+0075o-U+006Ft-U+0074e-U+0065d-U+0064"\"U+0022␣-U+0020C-U+0043:-U+003A\\\U+005C␣-U+0020c-U+0063a-U+0061f-U+0066é-U+00E9␣-U+0020😀-U+1F600

encoded JSON string28 chars → 38 bytes"Tab\there \"quoted\" C:\\ café 😀"

" and \Always escaped, as \" and \\.control U+0000-001FMust be escaped. Tab, newline and five others have short forms like \t; the rest use \u00XX.other non-ASCIIAllowed as-is in UTF-8. ASCII-only output turns é into \u00e9.beyond U+FFFFEmoji and rare scripts. Escaped, they need a surrogate pair: 😀 is \ud83d\ude00.

~/spec-sheet

JSON, for reference.

Two documents define JSON and agree on the grammar: ECMA-404 and IETF RFC 8259, which adds the interoperability rules. Around them sits a family of stricter, looser and line-based variants.

Full nameJavaScript Object NotationSpecified by Douglas Crockford in the early 2000s

Extension.json.jsonl or .ndjson for one value per line

MIME typeapplication/jsonNo charset parameter: UTF-8 is implied; +json suffix for derived types

Apple UTIpublic.jsonUniform Type Identifier on macOS and iOS

StandardsECMA-404 · RFC 8259 · STD 90ECMA-404 2nd edition and RFC 8259 both published December 2017

EncodingUTF-8 onlyRequired for JSON exchanged between systems; no BOM

Value typesobject · array · string · number · true · false · nullNo dates, binary, comments, NaN or Infinity

Whitespacespace · tab · LF · CROnly these four, and only between tokens

Numbers-?int(.frac)?(e±exp)?No leading zeros, no leading +, no hex, no trailing dot

Top levelany valueSince RFC 7159; RFC 4627 allowed only an object or array

Strict profileI-JSON · RFC 7493No duplicate keys, no lone surrogates, numbers within double precision

Magic bytesnoneUsually starts with 7B “{” or 5B “[”, after optional whitespace

variantdifference from JSONdefined by

JSON5Comments, trailing commas, single quotes, unquoted keys, hex, Infinityjson5.org

JSONCJSON plus comments, used by VS Code settings and tsconfigMicrosoft

JSON LinesOne complete JSON value per line, for logs and streamsjsonlines.org

JSON-seqRecords prefixed with the RS control characterRFC 7464

JSON-LDOrdinary JSON with @context keys that link dataW3C

GeoJSONFixed shapes for points, lines and polygonsRFC 7946

JSON SchemaJSON that describes and validates other JSONjson-schema.org

2001First JSON messageCrockford and colleagues send JSON between browser and server at State Software.

2002json.orgThe grammar is published as railroad diagrams that still define it.

2006RFC 4627application/json is registered; top level must be an object or array.

2013ECMA-404Ecma publishes a short, syntax-only standard.

2014RFC 7159Any value allowed at the top level; interoperability advice added.

2017RFC 8259Becomes Internet Standard 90 and makes UTF-8 mandatory.

2019JSON ⊂ ECMAScriptES2019 lets U+2028 and U+2029 appear in string literals, so every JSON text is valid JavaScript.

~/next

ruleJSON validatorCheck syntax without reformatting account_treeJSON tree viewerBrowse nested data as a collapsible tree differenceJSON diffCompare two JSON payloads swap_vertBase64 encoder & decoderEncode text or decode Base64 strings linkURL encoder & decoderQuery strings, spaces and percent-encoding

150+FREE TOOL FOR SITE OWNERS · KALENUXSee exactly why Google isn't ranking your siteTechnical SEO checks in minutes: indexation, Core Web Vitals, broken links, meta, hreflang and structured data, each with the exact fix.Run my free auditarrow_forward

menu_bookreferences, the sources behind this page

01RFC 8259: The JSON Data Interchange FormatIETF 02Introducing JSONjson.org 03JSONMDN Web Docs 04JSON.stringify() (indentation)MDN Web Docs 05JSON.parse()MDN Web Docs 06ECMA-404: The JSON data interchange syntaxEcma International 07RFC 7493: The I-JSON Message FormatIETF 08Parsing JSON is a MinefieldNicolas Seriot 09json: JSON encoder and decoderPython docs 10Clipboard.writeText()MDN Web Docs 11BlobMDN Web Docs

Frequently Asked Questions

How do I format and beautify JSON?

Paste or type your JSON into the tool and it instantly reformats it with clean indentation and line breaks so nested structures are easy to read. You can adjust the indentation and copy the beautified result. Everything runs in your browser, so your data never leaves your device.

Does the JSON formatter validate my JSON?

Yes. As it formats, the tool checks that your JSON is well formed and points out errors such as missing commas or brackets, so you can fix invalid data quickly before using it in your code.

Is the JSON formatter free and private?

Yes, it is completely free with no signup or limit. Because formatting happens locally in your browser, your JSON is never uploaded to a server, which makes it safe for sensitive or internal data.

Can I minify JSON as well as beautify it?

The formatter is built to make JSON readable with configurable indentation. You can beautify messy or minified JSON into a clean, structured layout that is easy to scan and debug.