What is JSON?
A JSON validator checks whether your text is valid JSON according to the JSON standard (RFC 8259) and pinpoints the first syntax error — such as a missing comma, an unclosed bracket, a trailing comma, an unquoted key, or single quotes instead of double quotes. JSON (JavaScript Object Notation) is the standard format for APIs and configuration, so catching mistakes early prevents bugs. This tool validates JSON instantly and privately in your browser.
Runs locally: your JSON is validated in your browser and never uploaded.
How JSON works
The validator parses your text with a strict JSON parser:
- It reads the text according to the JSON grammar (objects, arrays, strings, numbers, booleans, null).
- If parsing succeeds, the JSON is valid.
- If it fails, the tool reports what and where the problem is, so you can fix it.
How to use
- Paste your JSON into the input box.
- The tool processes it instantly in your browser.
- Copy the result.
Examples
| Input | Result |
|---|---|
{"name":"Sam","age":30} | Valid |
{name:"Sam"} | Invalid — keys must use double quotes |
{"a":1,} | Invalid — trailing comma |
[1, 2, 3] | Valid |
Options explained
- Auto Update — Validates as you type, with no button press.
- Pretty Display — Shows the parsed JSON in a readable, formatted view.
Common uses
- Checking API request and response bodies.
- Validating configuration and data files before use.
- Catching syntax errors that break parsers.
Frequently asked questions
What makes JSON invalid?
Common causes: trailing commas, single quotes, unquoted keys, missing commas or brackets, and comments (JSON does not allow comments).
Can JSON keys use single quotes?
No. JSON requires double quotes around keys and string values.
Does JSON allow comments?
No. Standard JSON has no comments; remove them before validating.