Check request bodies
Validate JSON before sending it to a REST API, webhook endpoint, serverless function, or local test server.
Free browser tool
JSON Validator
The JSON validator checks whether a JSON document is syntactically correct. It is built for fast checks while working with API payloads, configuration snippets, exported data, and webhook examples. Paste the JSON, run validation, and the page will tell you whether the input can be parsed as valid JSON.
When the input is invalid, the validator shows the parser message and, when available, line or column context. This makes it easier to find missing quotes, trailing commas, unclosed arrays, or invalid values. The validation runs locally in your browser.
JSON validator
Paste JSON and check whether the syntax is valid.
What this tool does
A JSON validator answers a direct question: can this text be parsed as JSON? It does not judge whether the data is correct for your business rules, and it does not validate against a schema. Instead, it catches syntax problems that stop parsers from reading the document at all. That makes it useful before sending a request body, committing a config file, importing seed data, or pasting an example into documentation.
Most JSON problems are small but disruptive. A missing quote, a comma after the final property, an unclosed array, or a value such as undefined can cause an entire payload to fail. The validator gives a clear message as soon as parsing fails, and modern browser parsers often include position, line, or column context. That feedback is enough to fix many errors without opening a full editor.
Because the validator runs in the browser, it is fast enough for quick checks during development. It pairs well with the JSON Formatter when you want to both validate and make the document readable, and with JSON Diff when you need to compare two valid payloads after syntax issues are resolved.
Common use cases
Debug configuration files
Catch invalid syntax in package config, editor settings, import maps, or static data files before they break tools.
Clean copied examples
Examples copied from chat, docs, browser consoles, or issue trackers often include comments or JavaScript-only syntax.
Confirm exported data
Validate exported JSON before converting it to CSV, XML, or another format.
Example before and after
The first example has a trailing comma after the final property. Removing it makes the object valid JSON.
Invalid JSON
{
"name": "Ada",
"active": true,
}Valid JSON
{
"name": "Ada",
"active": true
}How to use
- Paste the JSON you want to validate.
- Click Validate JSON.
- Read the success message or fix the reported syntax error.
Common errors
Using undefined
JSON supports null, true, false, numbers, strings, arrays, and objects. It does not support undefined.
Copying JavaScript objects
A JavaScript object literal may look like JSON but still be invalid because of unquoted keys or comments.
Broken escaping
Backslashes inside strings must be escaped correctly. Invalid escape sequences make the whole document fail.
Mixed quotes
Double quotes are required around string values and object keys. Smart quotes from rich text editors also fail.
Why use this tool
Catch malformed JSON before sending it to an API.
Debug copied examples and config files quickly.
Validate data without setting up a local script.
Best practices
Validate before conversion
Converters should start from valid JSON. Validate first when the source is copied from an uncertain place.
Fix one error at a time
Parsers stop at the first syntax problem. Fix that issue, then validate again to find the next one.
Use schema validation separately
Syntax validation is not the same as checking required fields, value ranges, or object shapes.
Keep error messages visible
When sharing debugging notes, include the parser error and a short snippet around the broken location.
Related JSON tools
Related guides
How to validate JSON and fix common errors
A practical guide to JSON validation, parser messages, and the most common syntax mistakes developers run into.
Common JSON syntax errors
Trailing commas, bad quotes, comments, unclosed brackets, and undefined values are the JSON mistakes developers hit most often.
Best practices for working with API responses
API responses are easier to debug when you validate syntax, format payloads, inspect errors, and compare changes deliberately.
FAQ
What does JSON validation check?
It checks whether the input follows valid JSON syntax.
Does it validate a schema?
No. This tool checks JSON syntax, not JSON Schema rules.
Is my JSON sent to a server?
The tool runs in your browser and does not require login, a database, or server-side processing.
Can it find trailing commas?
Yes. Trailing commas are invalid JSON and will be reported as syntax errors.