JSON Validator
Validate JSON syntax in your browser and identify malformed input before using it in an API, configuration file or application.
JSON Validator online
Check whether a piece of text is valid JSON — parsed with the browser's strict parser, with the parser's own error surfaced when it is not — before the data reaches an API or config file.
How to use this tool
- Paste your JSON into the input box.
- Click Validate JSON. Valid input is confirmed; invalid input shows the syntax error the parser reports.
- Fix, re-check, and copy with confidence.
Common uses
Debugging a failing API request body, checking a hand-edited config file before deploying it, verifying a payload copied out of logs or documentation, and teaching the difference between JavaScript object syntax and real JSON.
How it works
Validation uses the same strict grammar your code will meet in production: double-quoted keys and strings only, no trailing commas, no comments, no single quotes, and numbers in JSON form. The checker hands your text to the browser's JSON parser untouched — if it parses, the document is valid JSON; if not, the parser's error message (which in modern browsers names the position) is shown so you can find the fault.
Worked example
Two near-identical inputs show the value of a strict check. {"name": "Ana",} fails: JSON forbids the trailing comma that JavaScript tolerates. {name: "Ana"} also fails: keys must be quoted. The document {"name": "Ana"} passes. Most "invalid JSON" in the wild is one of these three habits — trailing commas, unquoted keys, single-quoted strings.
Privacy and browser processing
Your JSON is checked in your browser with JavaScript — it is never uploaded or stored.
Frequently asked questions
Does valid here mean valid everywhere?
Yes for the grammar: the browser parser implements the JSON standard, and anything it accepts is standard JSON. Individual APIs may still reject a valid document for schema reasons — missing fields, wrong types — which is a separate check (see the JSON Schema Validator).
Where exactly is my error?
The result shows the parser's message; current Chrome and Edge include a position in that message. Counting to the position, the culprits are almost always a missing comma, an unescaped quote inside a string, or a trailing comma.
Why is the JSON from my JavaScript object invalid?
Object literals are not JSON: unquoted keys, single quotes, undefined, functions and trailing commas are all legal in code and illegal in JSON. Stringify the object (JSON.stringify) instead of copying its source text.
Can it validate huge files?
The parser handles multi-megabyte documents comfortably; the practical limit is pasting them into the box. For routine megabyte-scale validation a local command-line parser is more convenient.
Is my JSON uploaded?
No. Validation runs in your browser; nothing is sent anywhere.