Validate JSON online — check syntax, format, and debug with detailed error messages
Use this free JSON validator to check your JSON syntax instantly. Validate JSON online with detailed error messages showing the exact line and column where problems occur. Format and beautify JSON for better readability. 100% client-side — your data never leaves your browser.
Formatted JSON will appear here
string | "hello" (double quotes) |
number | 42, 3.14, -17 |
boolean | true, false |
null | null |
array | [1, 2, 3] |
object | {"key": "value"} |
| 'text' | Use "text" instead |
| {key: 1} | Use {"key": 1} |
| [1, 2,] | No trailing commas |
| undefined | Use null instead |
| // comment | No comments allowed |
JSON (JavaScript Object Notation) is a lightweight data interchange format. It's easy for humans to read and write, and easy for machines to parse and generate. JSON is language-independent but uses conventions familiar to programmers of the C-family of languages.
JSON is commonly used for APIs, configuration files, and data storage. It has largely replaced XML as the preferred format for web service data exchange.
JSON is built on two structures:
{}. Keys must be strings in double quotes.[]. Values are separated by commas.Values can be strings, numbers, booleans (true/false), null, objects, or arrays. This allows for nested data structures of arbitrary complexity.
"hello" is valid, 'hello' is not.{"name": "value"} not {name: "value"}.[1, 2, 3] is valid, [1, 2, 3,] is not.// or /* */ comments.null instead of undefined.0.5 is valid, 00.5 is not.This tool helps you validate JSON online quickly and accurately:
When an error is found, you'll see the exact line and column number, plus a description of what went wrong. This makes debugging malformed JSON much easier.
JSON (JavaScript Object Notation) is a lightweight data interchange format. It's easy for humans to read and write, and easy for machines to parse and generate. JSON is the most common format for API responses and configuration files.
Paste your JSON data into the input area above and click the Validate button. The tool will instantly check your JSON syntax and show either a success message or a detailed error with the exact line and column number where the problem occurred.
Common JSON errors include: using single quotes instead of double quotes, trailing commas after the last item, unquoted property names, missing commas between items, and using undefined or NaN values which are not valid in JSON.
Yes, completely safe. This JSON validator runs entirely in your browser using JavaScript. Your data is never sent to any server. All processing happens locally on your device.
No, standard JSON does not support comments. If you need comments in configuration files, consider using JSON5, JSONC (JSON with Comments), or YAML instead. This validator follows the strict JSON specification.
Validate only checks if your JSON is syntactically correct. Format validates and then reformats the JSON with proper indentation and line breaks, making it easier to read and debug.
When this validator detects an error, it shows the line and column number where the problem occurred. Common fixes include: adding missing quotes around strings, removing trailing commas, ensuring all brackets are properly closed, and using double quotes instead of single quotes.
JSON formatting (also called beautifying or pretty-printing) adds proper indentation and line breaks to make JSON data more readable. Minified JSON is compact but hard to read; formatted JSON is easier to understand and debug.