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JSON Validator

Check if JSON is valid, pinpoint syntax errors by line and column, and see a structure diagnostic, in-browser.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Paste or type your JSON into the input box.
  2. 2.Read the verdict instantly: green "Valid JSON" or a red error with the line and column where parsing failed.
  3. 3.For valid JSON, review the structure report (type, depth, key count) to sanity-check the shape of your data.

About JSON Validator

JSON Validator answers one question fast and precisely: is this JSON actually valid, and if not, exactly where does it break? Unlike a formatter, it does not beautify or minify your data — it focuses on correctness checking, error localization, and structural diagnostics, so you can debug an API response or config file without touching its formatting. If you need to pretty-print or compress instead, that is a separate job for a formatter; this tool deliberately leaves your text unchanged.

Validation runs on your browser's native JSON parser, which implements the ECMA-404 / RFC 8259 grammar. That means the verdict here matches what your JavaScript runtime, Node.js, and most JSON libraries will accept in production — no lenient guessing, no auto-repair. Standard JSON is strict, and that strictness trips people up constantly: object keys must be wrapped in double quotes, single quotes are illegal for both keys and strings, a trailing comma after the last array or object element is rejected, comments (// or /* */) are not part of JSON, NaN and Infinity are not allowed, and every bracket and brace must be balanced. These are the exact mistakes this validator is built to catch and explain rather than silently tolerate.

When JSON is malformed, the validator surfaces the parser's own error message and, wherever the engine provides it, the precise line and column of the failure — for example "Invalid JSON at line 3, column 7." That turns a vague "unexpected token" into a spot you can jump straight to in your editor. Different browsers word the message slightly differently (V8 in Chrome/Edge, SpiderMonkey in Firefox, JavaScriptCore in Safari), and the tool normalizes the position from whichever format the engine reports.

When JSON is valid, you get a structure report instead of a wall of green: the top-level type (object, array, string, number, boolean, or null), the maximum nesting depth, the total number of keys across all levels, how many objects and arrays it contains, and the character count. This is genuinely useful for spotting accidentally deep nesting, oversized payloads, or a response whose shape is not what your code expected. One caveat worth knowing: JSON numbers are read as IEEE-754 doubles, so integers beyond 2^53 lose precision — a validation "pass" confirms syntax, not that a huge id survived intact.

Everything happens locally in the page — your JSON is never uploaded to a server, which matters when you are validating tokens, credentials, or private API payloads. Deeply nested input is handled safely: even pathological structures are caught and reported rather than crashing the tool. Paste, read the verdict, fix, and repeat.

Methodology & sources

Validation uses the JavaScript engine's native JSON.parse (ECMA-404 / RFC 8259 compliant); syntax errors are surfaced with line/column where the engine provides them.

Frequently asked questions

What's the difference between this and a JSON formatter?
A formatter beautifies or minifies JSON. This validator focuses purely on correctness: it tells you whether the JSON is well-formed, points to the exact line and column of any syntax error, and reports structural stats like nesting depth and key count. It does not reformat your data.
Why is my JSON reported as invalid when it looks fine?
Standard JSON (RFC 8259) is strict. The most common culprits are single quotes instead of double quotes, unquoted object keys, a trailing comma after the last item, comments (which JSON does not allow), or an unbalanced bracket or brace. The error message and line/column point you to where the parser gave up.
Is my JSON sent to a server?
No. Validation runs entirely in your browser using its built-in JSON parser. Your data never leaves your device, so it's safe to check payloads that contain tokens or private information.

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