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DevCodivo

JSON Validator

Check whether JSON is valid and get precise error locations with line and column numbers.

Runs in your browser — your data never leaves your deviceFree, no sign-up
Validation summary

The validation result will appear here.

How it works

As you type or paste, the document is parsed with your browser’s native JSON engine. If parsing fails, the tool converts the engine’s character-offset error into a human-readable message with the line and column where the problem starts. Valid documents get quick statistics: value count, key count, maximum nesting depth and size.

Features

  • Live validation as you type, plus an explicit Validate button
  • Precise line and column reporting for the first error
  • Document statistics for valid JSON
  • Copyable validation result
  • An intentionally broken example to demo error reporting
  • 100% client-side — your JSON never leaves the browser

How to use

  1. Paste or upload JSON (or load an example).
  2. Read the status card: valid documents show statistics, invalid ones show the exact error location.
  3. Copy the summary if you need to report it (e.g. in a bug report).

Example

{
  "name": "DevCodivo",
  "valid": true,
  "items": [1, 2, 3]
}

Frequently asked questions

Is my JSON uploaded anywhere when I validate it?
No. Validation runs entirely in your browser with JavaScript. Nothing is sent to any server, stored, or logged.
What counts as valid JSON?
A valid JSON document is one value — an object, array, string, number, boolean or null — that follows the JSON standard: double-quoted strings, no trailing commas, no comments, and no unescaped control characters in strings.
Why does my JSON fail even though it looks fine?
The usual culprits are invisible issues: trailing commas before a closing brace, single quotes, unescaped double quotes inside strings, or literal tabs/newlines inside strings. The validator reports the exact line and column of the first error.
Does validation tell me if my JSON matches a schema?
This tool checks syntax only — whether the document is well-formed JSON. It does not validate against a JSON Schema (data types, required fields, and so on).
How large a document can I validate?
Documents up to about 10 MB validate instantly since parsing is native. Larger inputs are rejected with a clear message rather than hanging the page.

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