JSON Validator
Validate JSON syntax and find errors instantly.
Before you deploy a config file or parse an API response, confirm your JSON is syntactically correct. Utilitoo's JSON Validator checks your input against the JSON specification and reports exactly where problems occur, such as missing commas, unquoted keys, trailing commas, or mismatched brackets.
Developers reach for a validator when a fetch call returns unexpected null, when Terraform or Kubernetes configs fail to apply, or when a coworker sends a hand-edited export that will not load. Catching errors early saves hours of guessing which character broke the parser. QA teams also validate fixture files before automated tests run against them.
Paste suspicious JSON, run validation, and read the error message alongside your text. Fix the reported line, validate again, then pass the clean result to our JSON Formatter for readable output. If you are building client-side apps, validating before JSON.parse avoids runtime crashes in production.
Utilitoo processes everything in your browser. Your payloads, credentials, and internal data never touch our servers. The tool is free, requires no account, and is designed for backend engineers, frontend developers, DevOps teams, and data analysts who need trustworthy syntax checking. Whether you work with REST APIs, GraphQL responses, or static config files, a fast browser validator keeps your workflow moving without installing desktop tools or switching contexts.
Teams reach for JSON Validator when JSON arrives from APIs, logs, or config repos and needs a quick browser pass. Validate JSON syntax and find errors instantly. Chain Related Tools when you need a different representation after inspection.
Common use cases
- Checking webhook payloads from Stripe, GitHub, or custom integrations before deploying handlers.
- Verifying JSON exports from databases, spreadsheets, or NoSQL tools before ETL import.
- Debugging CI failures where a config file claims to be JSON but breaks the build.
- Teaching JSON syntax by showing exactly where a learner's document fails to parse.
- Gatekeeping formatted output - validate first, then pass to JSON Formatter or JSON Minifier.
Tips & common mistakes
Read the error message carefully: line and column numbers point to the first character the parser could not consume. Common fixes include double-quoting keys, removing trailing commas, and escaping backslashes in Windows paths. Valid JSON rejects undefined, functions, and comments - if you need those, the source is JavaScript, not JSON. On Utilitoo, validation runs entirely in your browser with no upload.
Common errors
- Unexpected token at position 0 - often a BOM, HTML error page, or XML pasted instead of JSON.
- Expected property name or '}' - unquoted keys or single quotes instead of double quotes.
- Unexpected non-whitespace character after JSON - extra data after a valid document, common when concatenating logs.
How to use
- Paste JSON into the input area.
- Click Validate to check syntax.
- Review any error messages with line details.
Frequently Asked Questions
How do I check if my JSON is valid?▼
Paste your JSON into Utilitoo's validator and click Validate. You will see a success message or a specific syntax error with location details.
Why does my JSON fail validation with a trailing comma error?▼
Standard JSON does not allow trailing commas after the last item in an object or array. Remove the extra comma and validate again.
Can this tool validate JSON with comments?▼
Strict JSON does not support comments. Remove // or /* */ comment blocks, or convert the file to JSONC before validating.
Is it safe to validate JSON containing passwords or tokens?▼
Yes on Utilitoo. Validation runs entirely in your browser. No data is transmitted or stored on external servers.
What is the fastest way to fix invalid JSON?▼
Read the error line number, fix that single issue, and re-validate. Repeat until the validator reports valid JSON, then format if needed.
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