JSON Syntax Checker

Worked example

Example: `{name: "test"}` fails—keys must be quoted as `"name"` in valid JSON.

When to use this

• Quick checks on copied API responses.
• Validating LLM-generated JSON.
• Teaching students common JSON mistakes.

Common examples

• Trailing comma error on last object property.
• Single quotes rejected—use double quotes.
• Unescaped newline inside a string value.
• Large config file validates after removing comments (JSONC ≠ JSON).
• Empty input vs {} — empty is invalid; empty object is valid.

Common mistakes

• Smart quotes from Word docs.
• BOM characters at file start.
• Mixing JSON with JavaScript object syntax.

How it works

Parses JSON with the browser JSON parser and reports syntax errors (and location hints when available). Validates structure only—not a schema/OpenAPI checker.

Limitations

Validates JSON syntax only. Schema, business rules, and duplicate keys are not checked unless noted.

Privacy and file handling

Your data stays on your device and is not uploaded.

Formula or method

JSON.parse on your device. Schema validation is out of scope; pair with a schema tool when you need type constraints.