Data Anonymizer

The 'Data Anonymizer' is a completely free, browser-based tool that automatically detects and replaces personal data patterns in CSV, JSON, and plain text files. It recognizes email addresses, phone numbers (fully compatible with Japanese mobile and landline formats), credit card numbers, My Number (マイナンバー, 12-digit Japanese national ID), IPv4 addresses, and postal codes (〒xxx-xxxx) using regular expression pattern matching, and replaces them with consistent anonymous values.

The same input value always maps to the same anonymized output (consistent replacement), preserving data structure and referential integrity—so if the same person's email appears in multiple places, it will be replaced with the same anonymous email everywhere, enabling post-anonymization data analysis without disruption.

Input format is auto-detected among CSV, JSON, and plain text, and you can either drag-and-drop files or paste text directly. Anonymization targets are individually selectable via checkboxes. Results include a before/after comparison preview and replacement statistics by category.

All processing runs entirely within your browser's JavaScript engine, so customer data and confidential information are never transmitted to any external server. Ideal for GDPR and privacy law compliance preparation, test data generation, privacy protection before data sharing, and anonymizing data for internal reports.