Paste a JSON object, array, string, number, boolean, or null. Processing stays in your browser.
Ready to validate
Paste JSON and click Validate JSON// validate json syntax and inspect errors instantly
Validate JSON syntax, find parse errors, format clean output, and inspect object stats instantly with a private browser-based JSON checker.
Paste a JSON object, array, string, number, boolean, or null. Processing stays in your browser.
Ready to validate
Paste JSON and click Validate JSONAdd a JSON payload, config snippet, API response, or data object.
Run the checker to catch parse errors, trailing commas, bad quotes, and malformed values.
Use the formatted result for debugging, docs, tests, or API payload review.
JSON Validator checks whether pasted JSON can be parsed correctly, then formats valid input into a readable, indented version. It is useful when an API, build tool, or app rejects a payload and you need to quickly find the syntax problem.
Yes. The browser tool validates and formats JSON locally. The PHP endpoint is included only as a fallback pattern for deployments that need an API route.
Yes. Valid JSON can be an object, array, string, number, boolean, or null. Objects and arrays are most common for API work.
It formats valid JSON and points to the likely error location for invalid JSON. It does not silently rewrite broken data because that can change meaning.
Standard JSON does not allow trailing commas after the final object property or array item, even though JavaScript object literals often do.
No. Standard JSON does not allow line or block comments. Remove comments or use JSONC only in tools that explicitly support it.
Yes. After validation succeeds, use the download button to save the formatted result as a .json file.
A JSON validator is a small debugging tool that checks whether a block of JSON follows the strict syntax rules required by parsers, APIs, databases, and configuration systems. JSON looks simple, but a tiny mistake can break an integration: one trailing comma, one single-quoted string, one missing colon, one unescaped line break, or one mismatched bracket can make the entire payload invalid. This tool gives you a quick way to paste a payload, run validation, and see whether the text can be parsed correctly.
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JSON is used almost everywhere in modern development. REST APIs return JSON responses, frontend apps store settings as JSON, build tools read JSON configuration files, and test suites often use JSON fixtures. Because JSON is a data format rather than a programming language, it is intentionally strict. Keys must be quoted with double quotes. Strings must use double quotes. Values must be valid JSON values, not JavaScript expressions. Comments are not allowed in standard JSON. These rules help different systems parse the same data consistently, but they also mean copied snippets can fail unexpectedly.
When a payload fails, the first problem is usually finding where the parser stopped. A good JSON syntax checker should do more than say “invalid JSON.” It should help you narrow the issue by reporting the parser message and estimating the line and column where the error occurs. This is especially useful for large API responses, package metadata, translated content files, or mock data copied from logs.
The most common JSON errors are easy to miss by eye. Trailing commas are accepted in many JavaScript contexts but invalid in JSON. Single quotes around keys or values are invalid. Unquoted keys are invalid. Raw tabs or newlines inside strings must be escaped. Missing commas between properties can make two valid lines fail together. Extra closing braces or brackets can also appear when a snippet is copied from a larger document. This validator highlights the parse failure and shows the source line so you can fix the original input intentionally.
Validation and formatting often go together. Once a JSON payload is valid, pretty printing makes the structure easier to inspect. Indented JSON helps you see nested objects, arrays, repeated fields, and value types. It also makes code review easier because each key appears on a separate line. This tool formats valid JSON with readable indentation and preserves Unicode characters and slash characters where possible, keeping the output useful for human review.
Many JSON snippets contain temporary tokens, internal IDs, user records, draft configuration, or API responses that should not be uploaded to random services. A browser-based validator is safer for everyday debugging because the main validation logic runs locally on your device. That makes it convenient for quick checks during development, support work, QA testing, and documentation writing.
A syntax validator only answers one question: is this valid JSON? It does not know whether your API expects a specific field, whether a number should be positive, whether an enum value is allowed, or whether a property is required. For those rules, use a JSON Schema validator. A syntax validator is the first step. A schema validator is the second step when structure and business rules matter.
Paste the raw JSON into the input box, validate it, then fix any reported syntax issue. Once it passes, copy the formatted output into your editor, issue tracker, API client, or test fixture. If the payload is large, use the stats panel to understand its rough size and shape. This workflow is faster than switching between an editor, terminal parser, and browser console, especially when you only need a quick confirmation.