What is JSON Validation?

Almost every frustrating JSON bug is a one-character mistake: a trailing comma after the last element, a single quote where a double quote belongs, an unescaped line break inside a string. This validator parses your document and, when something is wrong, tells you exactly where — the line, the column and the reason — instead of just saying invalid JSON.

Paste or drop your JSON and validation runs as you type. A clean result means the document parses strictly and is valid JSON that any parser will accept. When it fails, the error message pinpoints the position, so a five-thousand-line API response becomes a ten-second fix. Because the check is a real parse, passing here is a meaningful guarantee, not an approximation.

The tool distinguishes common failure modes: invalid format, a root value that is neither an object nor an array where one is required, or input that is a JavaScript literal — an unquoted key, say — rather than strict JSON. That last case trips up many developers pasting from JavaScript source files; object literals and JSON look alike but are not the same syntax.

Validation happens in your browser and the document is never sent anywhere, which makes it reasonable to validate payloads with tokens, customer data or internal configuration. If you only need to reformat valid JSON, use the prettify tool; if you need to know why something fails, this is the one.