Check JSON Syntax Errors

Finding JSON Syntax Errors

JSON has strict syntax rules that are easy to break when editing by hand. Unlike JavaScript objects, JSON requires double-quoted keys, double-quoted strings, no trailing commas, no comments, and no undefined values. Break any of these rules and your JSON won't parse.

Our syntax checker reports the exact line and character position of the first error, so you don't have to hunt through hundreds of lines. Common catches include: trailing commas after the last array/object element, single quotes, JavaScript-style comments, and NaN or undefined values that aren't valid in JSON.

This is essential when editing package.json, tsconfig.json, .eslintrc.json, VS Code settings.json, or any hand-edited JSON configuration file. One misplaced character breaks the entire file, and error messages from config parsers are often unhelpful.

Tips

• JSON keys must be double-quoted: {"name": "value"}, not {name: "value"}.
• JSON does not support single quotes, comments, trailing commas, or undefined.
• If editing tsconfig.json or .vscode/settings.json, those files actually support JSONC (JSON with Comments) — but standard JSON parsers won't accept them.
• Use a JSON-aware editor (VS Code, JetBrains IDEs) to catch syntax errors as you type.