Common JSON Syntax Mistakes (and Quick Fixes)

JSON looks simple until the comma bites you.

Frequent errors

• Trailing commas — illegal in strict JSON.
• Single quotes — strings must use double quotes.
• Unquoted keys — keys must be quoted strings.
• Comments — not allowed in JSON (use JSONC in editors, strip before APIs).

Paste broken payloads into the JSON Formatter to locate the first parse error line, then cross-check What Is JSON? for the grammar basics.