How to Format and Validate JSON (Developer Guide)

JSON is everywhere in web apps — API responses, config files, and logs. A single trailing comma or unquoted key can break parsing, so formatting and validation save real debugging time.

Common JSON mistakes

• Trailing commas after the last item in an object or array
• Single quotes instead of double quotes for strings
• Unquoted keys or comments (JSON does not support comments)
• Numbers with leading zeros or invalid escapes

Why pretty-print?

Minified JSON is fine in production, but indented JSON makes diffs readable and helps you spot nesting errors quickly during development.

Validate before you deploy

Run validation on sample payloads from third-party APIs. Catching invalid JSON early prevents runtime crashes and confusing 500 errors.