Free Online JSON Lint & Validator
JSON linting is the process of checking JSON data for syntax errors that violate the RFC 8259 standard. A single trailing comma or unquoted key can break JSON.parse() in production, causing API failures, config loading errors, and data corruption. Our free online JSON lint tool catches these issues instantly — before they reach your users.
Why You Need a JSON Linter
JSON is deceptively strict. While JavaScript is forgiving (allowing trailing commas, single quotes, and unquoted keys), JSON requires double quotes for all strings and keys, forbids trailing commas, and rejects comments. Developers frequently copy JavaScript object literals into JSON files and wonder why they fail. A JSON linter bridges this gap by catching these subtle errors immediately.
Common JSON Lint Errors
Trailing Commas
JavaScript allows commas after the last element, but JSON strictly forbids them. Our linter pinpoints the exact line and column.
Single Quotes
JSON requires double quotes (") for all strings and keys. Single quotes (') cause immediate parse failures.
Unquoted Keys
Object keys must be wrapped in double quotes. { name: "Alice" } is invalid JSON — it must be { "name": "Alice" }.
Comments
JSON does not support // or /* */ comments. Our linter flags these and suggests removing them.
Undefined Values
undefined is not a valid JSON value. Use null instead.
🛡️ Local-First Privacy
Your JSON is validated 100% in your browser. Zero server involvement means your API keys, production configs, and user data never leave your machine.
🔍 Precision Error Reporting
Most linters just say "invalid JSON." We tell you exactly where — line number, column position, and what type of error it is.
JSON Lint in CI/CD Pipelines
Add JSON validation to your build process to catch syntax errors before deployment. While this web tool is perfect for quick checks, you can also use jq or python -m json.tool in GitHub Actions to validate all .json files in your repository automatically.
Related Tools
After linting, you might want to format your valid JSON, validate against a JSON Schema, orcompare two versions to spot changes.