Free online JSON validator and syntax checker. Validate JSON data with detailed line-level error messages, structure summary with keys and types, and AI-powered error explanations. 100% browser-based with zero uploads.
100% browser-based — your data never leaves your device
Validate JSON data and detect syntax errors with detailed error messages and line numbers.
Copy your JSON data and paste it into the input textarea above.
Press the Validate button to check your JSON for syntax errors.
If errors are found, they are displayed with line numbers and descriptions. Fix and re-validate until your JSON is valid.
Drop a file here or click to browse
Ctrl+Enter to validate
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JSON Validator is a free online json tool that validate json data and detect syntax errors with detailed error messages and line numbers. It works entirely in your browser — no downloads, no installations, and no server uploads required. backend developers, frontend engineers, DevOps engineers use JSON Validator when they need a fast, privacy-respecting way to process json data without installing additional software. It supports capabilities such as detailed error messages, line number reporting, real-time validation. Additional features include local processing. Common use cases include validating json configuration files before deployment to production, debugging malformed api responses during development, checking json data integrity in etl pipelines and data migrations. All processing happens locally using modern browser APIs, which means your data never leaves your device. This makes JSON Validator ideal for working with sensitive data, proprietary code, or any situation where privacy matters.
JSON Validator is a free online json tool that helps you validate json data and detect syntax errors with detailed error messages and line numbers. Key capabilities include detailed error messages, line number reporting, real-time validation. All processing is done locally in your browser — no data is uploaded, stored, or shared with any server. There are no sign-ups, no file size limits, and no hidden charges. It is commonly used to validating json configuration files before deployment to production.
Copy your JSON data and paste it into the input textarea above.
Press the Validate button to check your JSON for syntax errors.
If errors are found, they are displayed with line numbers and descriptions. Fix and re-validate until your JSON is valid.
| Category | Details |
|---|---|
| Input Limits | Maximum file size: Browser memory bound (~2 GB) |
| Nesting depth: Unlimited (browser stack limit) | |
| Supported Formats | JSON, JSONC (with comments), JSON5 (extended syntax) |
| Browser Engine |
|
All operations run entirely in your browser using built-in JSON APIs. No server uploads, no data storage, and no third-party requests.
JSON Validator is ideal when you need to validating json configuration files before deployment to production without installing software or uploading data to a server. Since everything runs in your browser, there is no setup time and no risk of your data being stored on external servers. For for persistent editing environments with linting, consider using VS Code with JSON extension. For for server-side JSON processing in scripts, jq (command-line) may be a better fit. JSON Validator fills the gap between heavyweight desktop tools and insecure online services that require uploading your data.
The tool attempts to parse your input using JSON.parse(). If parsing fails, the error message shows the exact location and nature of the syntax problem.
Trailing commas, missing quotes, single quotes instead of double quotes, mismatched brackets, invalid numbers, duplicate keys, and more.
Yes. A validator checks for syntax errors. A formatter beautifies JSON. This tool focuses purely on validation, while our JSON Formatter & Validator does both.
Shows exact error location, error type, and suggested fix for invalid JSON.
Errors are reported with precise line and column numbers for quick debugging.
Optionally validate as you type with instant feedback on syntax correctness.
All validation happens locally in your browser. Your data never reaches any server.
JSON Validator is useful in a variety of scenarios across different workflows:
Validating JSON configuration files before deployment to production
Debugging malformed API responses during development
Checking JSON data integrity in ETL pipelines and data migrations
JSON does not allow trailing commas after the last element in an object or array. This is one of the most common JSON validation errors.
JSON requires all keys to be enclosed in double quotes. Single quotes and unquoted keys are invalid.
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