BYTETOOLS

JSON Validator

Free online JSON validator: validate JSON and find syntax errors with the exact line and column. See root type, key counts and depth — instant and 100% private.

What is the JSON Validator?

The ByteTools JSON Validator checks whether a document is valid JSON and tells you precisely where it breaks.

  • Instant valid / invalid verdict using the native JSON parser
  • Errors pinpointed with line and column numbers
  • Caret pointer marks the exact offending character
  • Shows root type, key/element counts and max nesting depth
  • Handles large documents smoothly
  • 100% private — nothing is sent to a server

How to use the JSON Validator

  1. 1

    Paste the JSON you want to check into the input box.

  2. 2

    Click Validate JSON.

  3. 3

    If it is valid, review the root type, key/element count, depth and size stats.

  4. 4

    If it is invalid, read the error and use the caret pointer to locate the exact line and column.

  5. 5

    Fix the input and validate again until it passes.

About the JSON Validator

The ByteTools JSON Validator checks whether a document is valid JSON and tells you precisely where it breaks. On failure you get the parser's error message translated into a line and column number, plus a caret pointer under the exact character in the offending line — no more hunting through minified payloads for a missing bracket.

When the JSON is valid, the validator summarizes the document: the root value type, how many keys or elements the root contains, the maximum nesting depth and the size in bytes. That quick profile helps you sanity-check API responses, config files and data exports at a glance.

Validation runs entirely in your browser using the native JSON parser, so your payloads are never uploaded anywhere. It is safe for tokens, credentials in config files and private customer data.

Frequently asked questions

How do I check if my JSON is valid?

Paste it into this online JSON validator and click Validate JSON. The tool runs it through the same strict JSON parser browsers use; you either get a green 'Valid JSON' panel with document stats, or the exact line and column where parsing failed.

Is this JSON validator free to use?

Yes. It is completely free with no sign-up, no ads in the workflow and no limit on how many documents you validate. Everything runs in your browser, so there are no server costs to pass on and nothing to install.

What are the most common JSON syntax errors?

Trailing commas after the last item, single quotes instead of double quotes, unquoted property names, comments, and unescaped control characters inside strings. JavaScript object literals allow these, but strict JSON does not.

How does the validator find the error's line and column?

The JSON parser reports the character position where it stopped. The validator converts that position into a line and column by counting line breaks, then prints the offending line with a caret (^) underneath the exact character so you can spot the problem immediately.

Is JSON with comments valid?

No. Standard JSON (RFC 8259) does not allow comments, so files with // or /* */ comments fail validation. Formats like JSONC and JSON5 accept comments, but you must strip them before using strict JSON parsers.

Can a JSON document be just a string or number?

Yes. Since RFC 7159, any JSON value — a string, number, boolean, null, object or array — is a valid document on its own. The validator shows the root type so you can confirm what you actually have.

Is my data uploaded when I validate it?

No. Validation happens entirely in your browser with JavaScript. The JSON is never transmitted, logged or stored, which makes the tool safe for API keys, personal data and other confidential payloads.

Guides for JSON Validator

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