YAML Validator

Validate YAML syntax with detailed line-number errors. Pretty-print and convert YAML to JSON. Free, private — all in your browser.

About YAML Validator

Validate YAML syntax, pretty-print messy files, and convert between YAML and JSON. Detailed error messages include line numbers and descriptions to help you fix issues fast. All processing happens in your browser — nothing is uploaded.

Free & Unlimited

Validate as much YAML as you need. No limits, no paywalls, no account.

100% Private

Your YAML never leaves your browser. No uploads, no servers, no tracking.

Instant Results

See validation errors with line numbers immediately. Fix and re-validate in seconds.

No Signup Required

Use it immediately. No registration, no email, no tracking.

📋 Common Use Cases

Email List Cleaning

Validate email addresses before sending campaigns. Remove invalid addresses, catch typos in domain names, and improve deliverability rates.

Phone Number Standardization

Normalize phone numbers from international customers into a consistent format. Ensure your CRM, dialer, or messaging system accepts every number.

Form Data Quality

Validate user-submitted data before storing it in your database. Catch errors at entry time rather than discovering them during analysis.

Database Migration Prep

Clean and validate data before importing into a new system. Find and fix format issues that would cause import failures.

🪜 How to Use This Tool

  1. Paste or upload your data
    Enter individual values or upload a file with multiple records. Most validators accept CSV, TSV, and plain text.
  2. Configure validation rules
    Set the level of validation, choose output format, or specify which checks to perform — syntax only, domain verification, or full deliverability.
  3. Review validation results
    See a summary of valid/invalid counts and per-record details. Invalid entries are flagged with the specific reason for failure.
  4. Export cleaned data
    Download validated records or fix issues directly. Separate valid and invalid entries for targeted cleanup.

📚 Related Guides

Frequently Asked Questions

Is this data tool free?▼
Yes. All data tools are completely free. No signup needed.
Is my data sent to a server?▼
No. All data processing happens in your browser. Your JSON, CSV, SQL, and text data never leaves your device.
Can these handle large files?▼
JSON formatter and CSV tools comfortably handle files up to ~10MB in browser. Performance depends on your device for larger datasets.