Pasting JavaScript object literals
JSON requires double-quoted keys and strings. Comments, single quotes, undefined, and trailing commas are valid in some JavaScript contexts but invalid in JSON.
JSON Validator | Validate & Debug JSON Syntax
FormattingRuns in Your Browser (No Uploads)
Validate JSON syntax in real time and pinpoint mistakes by exact line and column—catch trailing commas, unclosed braces/brackets, unquoted keys/strings, invalid escapes, and duplicate keys. Fast, private, and 100% in-browser.
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What to do next
Continue with a related workflow or open the next tool that usually follows this task.
Workflow guide
Convert CSV to JSON for spreadsheet data cleanup
Use this workflow when a spreadsheet export needs to become API-ready JSON, a fixture, or a structured dataset for debugging.
OpenRelated toolJSON Formatter and Validator Online | Format, Minify, Debug
Format, validate, and minify JSON with instant error highlights—fully local.
OpenHow to Use This Tool
- 1
Paste or type your JSON into the input area.
- 2
Use Live mode for instant validation or Manual mode to click “Validate”.
- 3
If invalid, read the message with the exact line and column to fix.
- 4
Correct the issue and see results update automatically.
- 5
Copy or use the validated JSON in your project.
When to Use This Tool
API Development & Debugging
Paste API requests/responses to catch malformed JSON before clients break.
Configuration File Validation
Verify package.json, tsconfig.json, and other config files before commit or deploy.
Data Validation & QA
Check imported/exported JSON for serialization or encoding issues.
Learning JSON Syntax
Practice writing valid JSON with instant feedback and error locations.
Common Mistakes
Ignoring duplicate keys
Some parsers accept duplicate object keys and keep the last value. Treat duplicate keys as a data quality problem before using the payload in tests or APIs.
Validating only the changed fragment
A small fragment can be valid while the surrounding file is broken. Validate the complete object or array that your application will actually parse.
Examples
Find a trailing comma in an API fixture
A copied response fails because the last property still has a comma. The validator points to the exact line before the fixture reaches a test suite.
Input
{
"status": "ok",
"count": 3,
}Output
Invalid JSON: remove the trailing comma after "count": 3.Check a config file before deployment
Validate a package, tsconfig, or app settings file locally so unclosed braces and bad escaping are caught before CI or production parsing.
Input
{"feature":"ads","enabled":true,"paths":["/en/tools"]}Output
Valid JSON with one object, one boolean field, and one paths array.JSON Syntax & Validation (RFC 8259)
JSON (RFC 8259) requires double-quoted keys/strings, escaped control characters, no comments, and no trailing commas.
The validator uses a compliant parser and maps exceptions to line/column positions with actionable messages.
All validation runs client-side for speed and privacy.
Frequently Asked Questions
Q.What JSON syntax errors can this validator detect?
A. All RFC 8259 syntax violations including trailing commas, unclosed braces/brackets, unquoted keys/strings, invalid escapes, duplicate keys, unexpected tokens, and more.
Q.Does this tool format or beautify JSON? How is it different from a JSON Formatter?
A. No. This tool focuses on syntax validation only. For pretty-printing or minifying, use a JSON formatter.
Q.Can this validator handle very large JSON files? Any size limits?
A. Yes—within browser memory limits. Inputs up to a few megabytes typically validate instantly; very large files may benefit from Manual mode.
Q.What's the difference between JSON and JavaScript objects?
A. JSON is a strict text format (RFC 8259). JavaScript objects are runtime structures that can include types not allowed in JSON (e.g., functions, undefined, Symbols).
Related workflow guides
Use these focused guides when you need a practical workflow before opening the tool.
Workflow guide
Convert CSV to JSON for spreadsheet data cleanup
Use this workflow when a spreadsheet export needs to become API-ready JSON, a fixture, or a structured dataset for debugging.
Workflow guideFix CSV and JSON conversion errors
Use this workflow when a spreadsheet export, API fixture, or CSV/JSON handoff fails because columns shift, headers disappear, characters look broken, or JSON will not parse.
Workflow guideFormat JSON for API debugging
Use this workflow when an API response is hard to read, a JSON payload fails validation, or a frontend error points to malformed structured data.
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