JSON Tools
JSON Validator
Strict RFC-8259 JSON validation with line / column on errors.
JSON input
About this tool
Paste JSON to validate. Tells you exactly where the parser failed (e.g. unexpected token at line 4 column 17) so you can fix syntax fast.
FAQs
What is JSON?
JSON (JavaScript Object Notation) is a lightweight text format for structured data - objects, arrays, strings, numbers, booleans, null. Defined in RFC 8259.
What makes JSON valid?
Strings in double quotes, no trailing commas, no comments, only the four primitive types plus objects and arrays.
How is JSON different from JavaScript object literals?
JS object literals allow single-quoted strings, unquoted keys, comments, trailing commas. JSON allows none of those.
Does the validator catch duplicate keys?
JSON.parse silently keeps the last duplicate. RFC 8259 says duplicate keys are 'unpredictable' - avoid them.