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JSON Validator Online — Lint & Check JSON Syntax

Free, browser-based JSON validator. Instantly check JSON syntax for errors with precise line and column indicators. Your data never leaves your browser.

What is a JSON Validator?

A JSON validator (also called a JSON linter or syntax checker) is a developer utility that analyzes a JSON string to determine if it strictly adheres to the official JSON specification. If the JSON is invalid, the validator identifies the exact position of the syntax error.

This tool runs entirely in your browser using JavaScript. No data is transmitted to an external server, keeping your payloads completely secure and private.

Features

  • Instant inline validation as you type
  • Highlights errors with line and column numbers directly in the editor gutter
  • Handles large JSON payloads (up to 5 MB) efficiently
  • Fast and reliable parsing using native JavaScript APIs

How to use this JSON Validator

  1. Paste your JSON: Drop your JSON text into the editor.
  2. Review errors: If your JSON contains a syntax error, the linter will instantly display a red marker in the gutter, and a precise error message will appear below the editor.
  3. Fix and retry: Correct the mistake. Once valid, you’ll see a green success message confirming your JSON is properly structured.