// Valid JSON
✅ Valid JSON{
"name": "John",
"age": 25,
"active": true
}JSON Validator
Check JSON syntax with line-aware error reporting. Valid input is shown in the output panel; invalid input shows exactly where it broke.
JSON input
Status
Why validate JSON?
JSON is the standard data format for APIs, configuration files, and data exchange between systems. A single syntax error — a trailing comma, an unquoted key, or a missing bracket — can break an entire application. Validating JSON before deploying ensures your API responses, config files, and data payloads are syntactically correct.
This validator uses the browser's native JSON.parse() method to check your input. If parsing succeeds, the JSON is valid. If it fails, the error message includes the exact position where the syntax error occurred, along with a clear hint about the most likely cause.
Common JSON syntax errors.
Trailing commas. JSON does not allow trailing commas after the last element in an array or object. This is the most common error — JavaScript allows it, but strict JSON does not. Remove the comma after the final entry.
Unquoted keys. All property names in JSON must be double-quoted strings. Writing { name: "John" } is invalid; it must be { "name": "John" }. This validator catches unquoted keys instantly.
Single quotes. JSON requires double quotes for all strings. Single-quoted strings are not valid JSON. If you're coming from JavaScript, this is a common gotcha.
Comments. JSON does not support comments of any kind. Using // or /* */ will cause a parse error. Remove all comments before validating.
How to validate JSON in your workflow.
API debugging. When debugging API responses, paste the response body into this validator to confirm it's valid JSON before investigating logic issues. Many API errors are caused by malformed JSON responses.
Configuration files. Validate package.json, tsconfig.json, and other configuration files before committing. A syntax error in these files can prevent your build tools from running.
Data migration. When migrating data between systems, validate the JSON at each step to catch corruption early. Invalid JSON in a migration pipeline can silently drop records.
JSON vs JSON5 vs JSONC.
Strict JSON doesn't allow comments, trailing commas, unquoted keys, or single-quoted strings. JSON5 relaxes these rules, adding support for comments, trailing commas, unquoted property names, and single-quoted strings. JSONC (used by tsconfig.json) allows comments but otherwise follows standard JSON syntax. If your file uses one of these relaxed formats, it may fail standard JSON validation even though it's valid in its intended format.
When this validator reports an error, check whether your file is supposed to be JSON5 or JSONC. If so, the "error" may actually be valid syntax for that format. Consider using a format-specific validator for those cases, or strip comments and trailing commas before validating against strict JSON.
Best practices for valid JSON.
Use a linter. Tools like ESLint with the eslint-plugin-json rule, or dedicated linters like jsonlint, catch syntax errors as you type. Configure your editor to show JSON errors in real time so you never commit invalid files.
Automate validation. Add a JSON validation step to your CI pipeline. A simple script that runs JSON.parse() on every JSON file in the repository catches issues before they reach production. This is especially important for configuration files that control build and deployment behavior.
Use schema validation. Syntax validation confirms the JSON is structurally correct, but schema validation confirms it has the right shape — required fields, correct types, valid values. Libraries like Ajv (JavaScript), jsonschema (Python), and Newtonsoft.Json (C#) let you define a JSON Schema and validate data against it.
Prefer tools that output JSON. When building APIs, use your language's JSON serializer rather than manually constructing JSON strings. Manual construction is error-prone — missing a comma or quote is easy to do. Let the serializer handle escaping, formatting, and structural correctness.
Your input is processed locally and isn't uploaded for processing. Verify by opening DevTools → Network — there are no requests carrying your data.
JSON Validator examples.
// Invalid: trailing comma
❌ Invalid JSON — unexpected token at position 34{
"name": "John",
"age": 25,
}// Invalid: unquoted key
❌ Invalid JSON — expected double-quoted property name{ name: "John" }Frequently asked questions.
What is a JSON validator?
A JSON validator checks whether a text string is syntactically correct JSON. It detects errors like missing quotes, trailing commas, unclosed brackets, and reports the exact line and column where the problem occurs.
What is the best JSON validator online?
This free online JSON validator runs entirely in your browser with no data upload. It provides instant syntax checking with line-by-line error reporting. For schema validation, tools like jsonschema.net or Ajv are recommended.
How to use a JSON validator?
Paste your JSON into the input panel. The validator instantly checks syntax and shows "Valid JSON" or an error message with the exact line and column where parsing failed.
How to validate JSON schema?
For JSON Schema validation, use libraries like Ajv (JavaScript), jsonschema (Python), or online tools like jsonschema.net. This validator checks syntax only — schema validation is on our roadmap.
How to validate JSON in Python?
Use json.loads(data) to check syntax — it raises JSONDecodeError on invalid JSON. For schema validation, use the jsonschema library: jsonschema.validate(instance, schema).
How to validate JSON in VS Code?
VS Code validates JSON automatically when you open a .json file. Red squiggly lines indicate errors. You can also paste into this online validator for detailed error reporting.
What is the difference between JSON validator and formatter?
A validator checks if JSON syntax is correct and reports errors. A formatter adds indentation and spacing to make valid JSON readable. This tool focuses on validation.
Is my JSON data sent to a server?
No. Validation runs entirely in your browser using JavaScript. Your data never leaves your device — you can verify this by opening the Network tab in DevTools.
How does JSON validation work?
The validator parses your input using the browser's native JSON.parse() method. If parsing succeeds, the JSON is valid. If it fails, the error message includes the exact position where the syntax error occurred.
What does "unexpected token" mean?
This error means the parser found a character it didn't expect at that position. Common causes: trailing commas, missing quotes around keys/values, unclosed brackets, or comments (which JSON doesn't support).