Validate JSON syntax instantly and pinpoint structural errors with exact line-number precision.
Paste your JSON payload to instantly verify syntax, detect error coordinates, and inspect line numbers.
Paste or type your JSON into the editor above. The validator checks your input against the ECMA-404 standard and highlights any syntax errors with a red marker on the exact line where the problem originates. Use the Load Sample button to try an example, Prettify to format valid JSON with consistent indentation, or Copy to grab the contents to your clipboard.
JSON validation is the process of checking whether a text string is syntactically correct according to the ECMA-404 JSON Data Interchange Standard. Valid JSON must follow strict rules: all strings and property keys must use double quotes, values must be strings, numbers, booleans (true / false), null, objects, or arrays, and no trailing commas are allowed.
This is different from JSON Schema validation, which checks whether a valid JSON document conforms to a specific structure (required fields, value types, constraints). This tool focuses on syntax validation — ensuring your data is well-formed JSON that any parser in any programming language can read without errors.
These are the errors developers encounter most frequently when working with JSON data:
Every property in an object and every element in an array must be separated by a comma. A missing comma between items is the single most common JSON error. Equally, a trailing comma after the last item (such as {"name": "test",}) is invalid in strict JSON, even though JavaScript allows it.
JSON requires double quotes (") for all strings and property keys. Single quotes ('value') and unquoted keys ({name: "test"}) are valid in JavaScript but will fail JSON validation.
JSON does not support comments — neither // nor /* */. Additionally, JavaScript-specific values like undefined, NaN, and Infinity are not valid JSON. Use null for absent values instead.
Every opening { must have a matching }, and every [ must have a matching ]. Deeply nested structures make it easy to accidentally close with the wrong bracket type or leave a structure unclosed.
A JSON validatorchecks whether your data is syntactically correct — it answers the question “Is this valid JSON?” A JSON formatter takes valid JSON and reformats it with consistent indentation and line breaks for readability. They serve different purposes: validate first to catch errors, then format for readability. This tool combines both — it validates your input and offers a Prettify button to format valid JSON automatically.
Unlike many online JSON tools that process data server-side or offer shareable links that store your payloads publicly, this validator runs entirely inside your browser. No HTTP requests are made with your JSON data, nothing is logged, and nothing is stored. You can verify this by checking the Network tab in your browser's developer tools while using the validator. This makes it safe for API keys, internal configurations, authentication tokens, and any sensitive production data.
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Copy your JSON payload from an API response, configuration file, or code editor and paste it into the editor above.
The validator instantly parses your input. Valid JSON shows a green confirmation. Invalid JSON highlights the error line with a red marker and icon.
Check the error panel for the exact line number, error type, and a suggested fix for the detected syntax issue.
Correct the highlighted error in the editor. The validator re-checks automatically so you can confirm the fix immediately.
Designed to save time, protect your privacy, and deliver professional-grade results every time.
Pinpoints the exact line and column where a syntax error originates, not just where the parser fails downstream — eliminating guesswork in large payloads.
Enforces the official JSON interchange standard. Catches subtle issues that lenient JavaScript parsers silently accept, such as trailing commas and single-quoted strings.
Validation runs in milliseconds with actionable error messages and suggested fixes, so you can iterate without waiting or switching between tools.
Every operation runs locally in your browser with zero network transmission. Safe for API keys, authentication tokens, and sensitive production data.
See how different professionals leverage this tool in their daily workflows.
Paste raw API responses to verify their structure before parsing in your application. Quickly identify malformed output from third-party endpoints.
Validate package.json, tsconfig.json, appsettings.json, or any JSON config file before deploying changes to production environments.
Check the structural integrity of outgoing webhook payloads to ensure receiving services can parse them without errors.
Verify JSON exports from databases or ETL pipelines before importing into target systems to prevent data corruption during migrations.
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Everything you need to know about this tool.
A JSON validator is a tool that checks whether a text string conforms to the JSON syntax standard defined by ECMA-404 and RFC 8259. It verifies that brackets and braces are properly matched, all strings use double quotes, property keys are quoted, and no trailing commas or invalid values exist. This validator also reports the exact line and column number of each error to help you fix issues quickly.
Paste your JSON content into the editor above. The validator runs automatically and highlights any syntax errors with a red marker on the exact line. You can also use the Load Sample button to try example data, or the Prettify button to format valid JSON with consistent indentation.
The most frequent JSON errors are: missing commas between properties or array elements, trailing commas before closing brackets or braces, using single quotes instead of double quotes, leaving property keys unquoted, including comments (JSON does not support comments), and using JavaScript-specific values like undefined, NaN, or Infinity.
No. The official JSON specification (ECMA-404 and RFC 8259) does not allow comments — neither single-line (//) nor multi-line (/* */). If you need comments in configuration files, consider JSONC (JSON with Comments) or JSON5, which are supported by tools like VS Code but are not standard JSON.
JSON validation checks whether a string is syntactically valid JSON — correct brackets, quotes, commas, and data types. JSON Schema validation goes further by verifying that a valid JSON document matches a specific structure, such as requiring certain fields, enforcing data types, or restricting value ranges. This tool performs syntax validation.
With this tool, yes. All parsing and validation runs entirely inside your browser using JavaScript. Your JSON data is never sent to any server, stored, or logged. You can verify this by opening your browser developer tools (Network tab) and confirming zero outbound requests during validation.
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