About the JSON Syntax Validator
Check whether a document follows JSON syntax and display parser errors.
Formula or method
Use the browser's strict JSON parser and show line and column where available.
Worked example
{"active":true} is valid; {active:true} is not.
How to use the tool
- Paste the JSON document or import a local text file.
- Inspect the validity status and any reported line/column position.
- Correct malformed delimiters or quotes, then copy the validated content if needed.
When this tool is useful
Check whether a JSON document parses correctly before using it in an app or API.
What to check before relying on the result
Valid JSON syntax does not guarantee that an API accepts its field names, types or schema.
Assumptions and limitations
It does not check JSON Schema rules or duplicate keys.
Frequently asked questions
Can JSON have trailing commas?
No. Trailing commas are not valid JSON.
Does valid JSON mean my API request is correct?
Not necessarily. APIs can require a particular schema or authentication; this tool checks JSON syntax only.
Continue with a related workflow
Privacy and support
Your inputs are processed locally in your browser. ToolMosaic does not upload or store the values you enter in this tool. Our tools are free, and we appreciate your support.