Data Deduplicator

About Data Deduplicator

Data Deduplicator is a powerful online tool that identifies and removes duplicate rows from CSV and JSON files. Select which columns to check for duplicates, choose whether to keep the first or last occurrence, and export clean data with unique records only. All processing happens locally in your browser for complete privacy.

How does duplicate detection work?

The tool compares rows based on the columns you select (key columns). If two or more rows have identical values in all selected columns, they are considered duplicates. You can choose to compare all columns or only specific ones, making it flexible for different data cleaning scenarios.

What's the difference between keeping first vs last occurrence?

When duplicates are found, you can choose which copy to keep. 'Keep first occurrence' retains the first row that appears in the file and removes subsequent duplicates. 'Keep last occurrence' keeps the most recent duplicate and removes earlier copies. This is useful when newer data should replace older entries.

Is my data secure?

Yes. All deduplication processing happens locally in your browser using JavaScript. Your files never leave your device, ensuring complete privacy for sensitive datasets like customer records, financial data, or confidential lists.

What file formats are supported?

Data Deduplicator supports CSV files (with various delimiters: comma, semicolon, tab, pipe) and JSON files (arrays of objects). Both formats can be deduplicated and exported to either CSV or JSON format after processing.

Can I see which rows were duplicates?

Yes. The tool provides two separate views: Unique Records (rows that will be kept) and Duplicate Records (rows that were removed). This lets you review both datasets before downloading, ensuring the deduplication worked as expected.

What does case-sensitive comparison do?

When enabled, 'Apple' and 'apple' are treated as different values. When disabled (default), uppercase and lowercase letters are considered identical. This is useful when your data may have inconsistent capitalization but you want to treat similar entries as duplicates.