Duplicate List Items

Free Duplicate List Finder

Paste any list and instantly see which items appear more than once — along with an exact occurrence count for each duplicate. No spreadsheet formulas, no scripting, no sign-up required. Everything runs in your browser, so your data never leaves your device.

How to Use

1. Paste your list into the text area (one item per line).
2. Click Find Duplicates.
3. Review the results — each duplicate is shown with how many times it appears.

Why Duplicate Data Is a Problem

Duplicate entries are one of the most common data quality issues and can cause real business problems. A duplicated email address means a customer receives the same message twice, which hurts your sender reputation. A duplicated product SKU leads to inventory miscounts. A duplicated row in a dataset skews aggregations, averages, and reports. Catching duplicates early — before you import into a CRM, database, or analytics tool — saves time and prevents costly errors downstream.

Common Uses

• Email lists — find addresses that appear more than once before sending a campaign
• CRM imports — detect duplicate contacts or company names before uploading to Salesforce, HubSpot, or similar tools
• Product catalogs — spot repeated SKUs or product names in an exported spreadsheet
• Survey responses — check for duplicate participant IDs or entries
• Code reviews — verify that a list of IDs, keys, or values is unique

Occurrence Count Explained

The result shows each duplicate value followed by its total count in parentheses — for example, London (3). This tells you not just that an item is duplicated, but exactly how many times it occurs, so you know the scale of the problem at a glance.