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JSON Validator Online
Last updated
The online JSON validator checks JSON syntax client-side against RFC 8259 specifications. It detects parsing errors—including unquoted keys, trailing commas, single-quoted strings, and unmatched brackets—highlighting the exact line and character column. The validator processes data entirely in browser memory, ensuring your proprietary API payloads and configuration files remain completely confidential.
Validate, inspect, and lint JSON data in real time with line-by-line syntax error detection. Instantly locate missing quotes, trailing commas, unmatched brackets, or unescaped characters with exact line and column coordinates. Format valid JSON with customizable 2-space or 4-space indentation, inspect object structure, and copy clean output with zero server uploads.
Runs in your browser
Your files and text are processed locally in your browser and are not uploaded.
How Do I Validate JSON Syntax and Identify Parse Errors?
- Paste or type your raw JSON payload into the input editor box.
- Click the Validate JSON button or toggle validation mode.
- If the JSON is invalid, view the red diagnostic alert displaying the exact error message, line number, and column position.
- Click Format JSON or Minify to transform valid syntax into structured 2-space indented trees or compact one-line strings.
- Use Copy to Clipboard to quickly paste the validated JSON into your code, terminal, or API testing tool.
Common JSON Syntax Errors and How to Fix Them
JSON (JavaScript Object Notation) is governed by strict grammar rules defined in RFC 8259. Common mistakes include: - Trailing commas: Placing a comma after the final key-value pair or array item (e.g. `{"a": 1,}`) is strictly prohibited in standard JSON - Single quotes: JSON requires double quotation marks (`"`) around all keys and string values; single quotes (`'`) trigger fatal syntax errors - Unquoted object keys: While JavaScript object literals permit unquoted keys (`{ name: "test" }`), valid JSON mandates double quotes (`{ "name": "test" }`) - Unescaped control characters: Raw tabs, newlines, or unescaped backslashes inside string values must be properly escaped (`\n`, `\t`, `\\`) - Dangling decimals and leading zeros: Numbers must follow strict numeric formats; `.5` or `05` are invalid, whereas `0.5` is valid
Pinpointing Errors with Line and Column Coordinates
Finding a misplaced bracket or comma in a 5,000-line JSON payload manually is tedious and error-prone. Our validator parses the string and extracts character offsets when a parsing exception occurs.
By mapping character offsets to row and column coordinates, the tool gives you actionable feedback like `Error at line 42, column 18: Unexpected token }`. You can jump directly to the defect and fix it in seconds without guessing.
Security & Privacy for Confidential JSON Payloads
Developers frequently need to debug JSON containing confidential production configurations, customer records, database dumps, JWT tokens, or API secrets. Using cloud-based JSON validators uploads your proprietary payload to external servers where it may be retained in server logs or proxy caches.
Our JSON validator executes entirely within your browser client. The validation logic uses browser JavaScript engine parsing (`JSON.parse`) in an isolated sandbox. No data leaves your machine.
Frequently asked questions
How do I validate JSON syntax online?
Paste your JSON text into the input field and click Validate JSON. The tool tests the syntax in real time, confirming valid JSON or reporting the exact line and column of any syntax errors.
Why is my JSON invalid with a trailing comma error?
Standard JSON (RFC 8259) prohibits trailing commas after the last element in arrays or objects. Removing the comma after the final property resolves the error.
Does this validator support large JSON files?
Yes. Because validation runs natively in your browser using V8's optimized JSON parsing engine, files up to several megabytes validate almost instantaneously.
Can I format and minify JSON after validating it?
Yes. Once your JSON is valid, click 2 Spaces or 4 Spaces to prettify the structure, or click Minify to strip all whitespace for production transmission.
Is my JSON payload kept private and confidential?
Yes. All validation and formatting happens purely in your browser. No JSON text, environment variable, or API key is ever uploaded to any server.
Need a different size? Use the full JSON Formatter.