Overview
This tool checks JSON structure against the parser rules used by modern applications. It is useful when you need to confirm that objects, arrays, strings, numbers, booleans, and null values are written in valid JSON form. When the input is invalid, the result points to the first issue so you can fix the exact character or line that breaks parsing. That makes it easier to catch missing commas, unescaped quotes, trailing commas, and bracket mismatches before you pass data to an API, config file, or script. Use it as a direct sanity check when copying payloads, editing request bodies, or reviewing exported data. It helps you separate valid JSON from text that only looks similar.
Use cases
- API request body reviewConfirm that a POST payload is valid before sending it to an endpoint, especially when nested objects and arrays are involved.
- Configuration file verificationCheck app settings, feature flags, or environment config exported as JSON so one typo does not break startup.
- Webhook payload inspectionValidate sample webhook data copied from logs or test events before mapping fields in another system.
- Data export cleanupDetect broken exports from dashboards or scripts where an extra comma, quote, or bracket slipped into the output.
How it works
- 1
Paste JSON into the input field.
- 2
The parser checks the text and reports whether it is valid.
- 3
If there is an error, review the position and fix the syntax before checking again.
Examples
Valid nested object
Input: {"user":{"id":42,"roles":["admin","editor"],"active":true}}
Output: Valid JSON
A complete object with nested data types, booleans, and an array.
Missing comma between fields
Input: {"name":"Mina" "age":29}
Output: Invalid JSON: expected a comma after "Mina"
Shows how a small punctuation mistake stops parsing.
Trailing comma in array
Input: {"items":["a","b",]}
Output: Invalid JSON: trailing comma is not allowed
Illustrates a common mistake when editing arrays by hand.
FAQ
What does this validator check first?
It checks whether the text is valid JSON syntax. If parsing fails, it reports the first point where the structure breaks, such as a missing comma, unmatched bracket, or unclosed string.
Why does a string with single quotes fail?
JSON requires double quotes for strings and property names. Single quotes are valid in JavaScript objects, but not in JSON text.
Does a trailing comma count as valid?
No. JSON does not allow trailing commas in arrays or objects, even if some programming languages tolerate them in their own syntax.
How should I read the error location?
Start at the reported line or character position and inspect the surrounding punctuation, quotes, and brackets. The real issue is often just before the marked spot.
Can valid-looking text still fail validation?
Yes. Text may look formatted correctly but still fail because of an unescaped quote, a missing colon, a control character, or a number written in an unsupported form.