RealJSON
Try now

JSON Validator

Validate JSON syntax and get clear error messages with position information.

Paste JSON to validate

In short: A JSON validator checks whether a piece of text follows the JSON specification exactly — and if it doesn't, tells you precisely where it breaks. Paste your JSON into RealJSON's validator and get an instant pass/fail result with the exact line and character position of any syntax error, all processed locally in your browser.

What is a JSON Validator?

JSON validation is the process of checking whether a piece of text is valid JSON — meaning it follows the JSON specification exactly: quoted keys, no trailing commas, properly escaped strings, and a single root element. A JSON validator automates this check and reports the exact location of any error.

RealJSON's free online JSON validator gives you instant feedback with detailed error messages and precise position indicators. Paste your JSON and know within milliseconds whether it's valid — and exactly what to fix if it isn't.

Why JSON Validation Matters

Invalid JSON is one of the most common causes of runtime errors in web applications. A missing comma between properties, an unquoted key, a trailing comma after the last array item, or a single quote instead of double quotes — any of these breaks JSON parsing and can cause your application to fail silently or throw an exception in production. Catching these errors early, before they reach your code or API, is far cheaper than debugging a live incident.

How JSON Syntax Checking Works

When you paste JSON into the validator:

  1. The parser attempts to parse the full document according to RFC 8259 (the JSON specification).
  2. If it succeeds, you see a green confirmation with a count of keys, values, and nesting depth.
  3. If it fails, you see the exact error: the type of syntax violation, the line number, and the character position — so you can fix it immediately.

Common JSON Errors the Validator Catches

Trailing comma e.g. [1, 2, 3,] — invalid JSON, a common mistake when editing arrays
Unquoted keys e.g. {name: "Jane"} — JSON requires double-quoted keys
Single quotes JSON requires double quotes; single quotes cause a parse failure
Missing colon Between key and value in an object literal
Unclosed brackets or braces An extra or missing ] or } at the end of the document
Invalid escape sequences Incorrectly escaped characters in string values
Duplicate keys Not strictly invalid but may silently lose data in some parsers

Frequently Asked Questions

How do I check if my JSON is valid?

Paste it into the validator. It parses the document instantly and either confirms it's valid with a stats summary, or shows the exact line and character position of the first error.

What does "Unexpected token" mean in a JSON error?

The parser hit a character it didn't expect at that position — commonly a trailing comma, a single quote, an unquoted key, or a missing colon or bracket. The validator points to the exact spot so you can fix it.

What kinds of errors can a JSON validator catch?

Trailing commas, unquoted keys, single quotes, missing colons, unclosed brackets or braces, and invalid escape sequences are among the most common syntax errors detected.

Is my JSON uploaded to a server when I validate it?

No. Everything runs in your browser using JavaScript — your JSON is never sent anywhere, so it's safe to validate API responses, configs, and other sensitive data.

What information do I get when my JSON is valid?

A confirmation appears along with a stats panel showing the number of keys, values, and the maximum nesting depth.

Related Tools

After validating, use the JSON Formatter to pretty-print your document, or the JSON Viewer to explore it as a collapsible tree. If you need to edit the JSON, the JSON Editor validates as you type.

Browse all free JSON tools →

Related tools

JSON Viewer JSON Formatter JSON Minifier JWT Decoder