Validation Tools

JSON Validator

Free JSON Validator to validate JSON syntax, find error line and position, format, minify, view a tree, and download JSON in the browser.

Free browser validation tool

JSON Validator

Paste or upload JSON, validate syntax, find helpful error details, inspect object and array counts, format readable JSON, minify, and review a tree view.

This tool validates format and structure only. It does not verify real-world existence or activity. Your data is processed locally in your browser.

Input

Paste, type, or load sample data.

Validation result

Ready.
Waiting

No validation yet. Add input and click Validate.

How it works

Validate format and structure without uploading data.

JSON Validator checks local input with browser JavaScript. It is built for quick format review, clear warnings, useful breakdowns, and privacy-focused daily work.

  1. Paste or type input Add the value, list, JSON, card format, password, or IBAN you want to validate.
  2. Choose validation options Enable normalization, duplicate removal, or related options when they apply to the current validator.
  3. Validate in your browser Click Validate or enable auto-validate to review format status, warnings, invalid parts, and detailed checks.
  4. Copy or download results Copy the validation result or download the report when useful for the workflow.

Why this free validator is useful

Clear checks, local processing, and helpful warnings.

Mirown validation pages explain what is checked, what is not checked, and where users should be careful. That makes the page more trustworthy for people and easier for search engines to understand.

  • Validate JSON syntax and show line and position when invalid
  • Detect common missing comma, invalid bracket, invalid quote, and trailing comma issues
  • Pretty format and minify JSON
  • Tree view for valid JSON with expandable structure
  • Show object count, array count, and nesting depth
  • Upload .json file and download output as .json
  • Copy formatted or minified JSON
  • Client-side only with no sign up

Best for

Common use cases for JSON Validator.

API debugging

Use this free browser validator for API debugging when you need a fast format check with no sign up.

configuration review

Use this free browser validator for configuration review when you need a fast format check with no sign up.

developer handoff

Use this free browser validator for developer handoff when you need a fast format check with no sign up.

data cleanup

Use this free browser validator for data cleanup when you need a fast format check with no sign up.

JSON syntax checks

Use this free browser validator for JSON syntax checks when you need a fast format check with no sign up.

Related validation tools

More free format checkers on Mirown.

Internal links connect the validation workflow so users can move from email, URL, JSON, card, password, and IBAN checks without searching again.

Email Validator Validate one email address or a pasted email list for structure, duplicate entries, common mistakes, disposable-domain warnings, and clean export.
URL Validator Check URLs, domains, paths, query strings, fragments, suspicious patterns, tracking parameters, and normalized output before sharing or importing links.
Credit Card Validator Check card number format only with local processing, masked preview, card brand detection, Luhn checksum, and format guidance for expiry and CVV fields.
Password Strength Checker Analyze password strength securely in your browser with a live meter, entropy estimate, checklist, common weak password warning, and improvement suggestions.
IBAN / Account Format Checker Validate IBAN format and structure only with country detection, length rules, MOD-97 checksum, normalized grouping, and bulk validation tables.

Frequently asked questions

Is Mirown JSON Validator free?

Yes. Mirown JSON Validator is free to use in your browser with no sign up or login required.

Does this validator check real-world existence?

This tool validates format and structure only. It does not verify real-world existence or activity. Your data is processed locally in your browser.

Is my input uploaded to Mirown?

No. These validation tools are frontend-only. JavaScript runs locally in your browser, and no backend or API is used for validation.

Can I use this for sensitive information?

The tool is privacy-focused and browser-only, but you should still review sensitive data carefully before pasting it into any website.