JSON Validator
Paste it. Validate it. Fix it.
Free Tool — No Login RequiredFormatted output will appear here…
Need Formatting?
Want to beautify your JSON with syntax highlighting?
Use our dedicated JSON Formatter for advanced indentation, syntax colours, and download options.
Validate JSON in 3 Steps
Paste or Upload
Paste your JSON directly into the editor or upload a .json file. Works with API responses, config files, schema markup, and any JSON data.
Instant Validation
Click Validate or enable Live Mode. Errors show the exact line number and column — no guessing where the problem is.
Format & Copy
If valid, see the formatted, syntax-highlighted output. Copy it, download it as .json, or minify it for production.
What is JSON Validation?
JSON validation is the process of checking that a JSON string strictly conforms to the JSON specification (RFC 8259). Valid JSON must use double quotes for all strings and keys, must not have trailing commas, must not contain comments, and must have perfectly balanced brackets and braces. Even a single misplaced comma or missing quote makes the entire JSON unreadable by browsers, APIs, and backend servers. A JSON validator parses your input using the same engine browsers use, and reports the exact location of any syntax error — saving you from manual character-by-character debugging.
Why Validate Your JSON?
- Find exact error location — line number and column, not just "invalid JSON"
- Prevent broken API requests caused by malformed JSON payloads
- Validate config files (package.json, .eslintrc, tsconfig.json) before committing
- Debug responses from REST APIs, GraphQL, and webhook payloads instantly
- Check JSON-LD schema markup before embedding it in your HTML pages
- Catch trailing commas — valid in JavaScript but illegal in the JSON spec
- Verify JSON before storing it in databases or passing to third-party services
- 100% browser-based — your data never leaves your device
Common JSON Errors
Trailing Commas
A comma after the last item in an object or array is valid JavaScript but illegal in JSON. The most common mistake when hand-editing JSON.
{"name": "John",} ← invalid
Single Quotes
JSON requires double quotes for all strings and property keys. Single quotes are valid in JavaScript but will break any JSON parser.
{'name': 'value'} ← invalid
Unquoted Keys
Unlike JavaScript objects, JSON requires all keys to be enclosed in double quotes. Bare keys without quotes are a syntax error in JSON.
{name: "value"} ← invalid
JSON FAQ
Common questions about JSON validation.
A JSON Formatter only reformats valid JSON with proper indentation and syntax highlighting. A JSON Validator checks whether your JSON is syntactically correct and reports exact errors with line numbers. This tool does both — it validates first, then formats and highlights the result.
No. All validation and formatting happens entirely in your browser using JavaScript's native JSON.parse() engine. Your data is never transmitted to any server.
The JSON specification (RFC 8259) was designed to be simple and unambiguous. Trailing commas were intentionally excluded to keep parsing straightforward. JavaScript allows them in object and array literals, which causes frequent confusion when developers treat JS objects and JSON interchangeably.
It means the parser found a character it did not expect at that position. This typically indicates a missing comma, an extra comma, an unquoted key, a single quote instead of a double quote, or a value that is not a valid JSON type such as undefined or a function.
The JSON is incomplete — a bracket or brace was opened but never closed. Check that every { has a matching }, every [ has a matching ], and that all strings are properly closed with a double quote.
Yes, functionally. JSONLint is a well-known JSON validator. This tool performs the same syntax checking using the browser's native JSON parser, with the same line-specific error reporting, plus formatting, minify, and file download options — all free, with no login required.
Yes. The tool handles JSON files up to several megabytes in modern browsers without performance issues. For files over 10MB, consider validating via command line: node -e "JSON.parse(require('fs').readFileSync('file.json','utf8'))"