Remove duplicates from a CSV file
To remove duplicate rows from a CSV, open the duplicate remover in Sigmera, choose whether to match on the whole row, ignore case and spacing, and preview the flagged duplicates before downloading the cleaned file. Sigmera does this entirely in your browser — your data is never uploaded to a server, so it’s GDPR-safe by design.
Last updated: June 2026
Use the duplicate remover free in your workspace
Free account, no credit card — every tool, unlimited rows, 3 free downloads a month, nothing uploaded.
🔒 Everything runs in your browser — your file is never uploaded, and the workspace even works offline once it has loaded.
Ways to remove duplicate rows, compared
| Method | Data uploaded? | GDPR-safe | Signup needed | Skill needed |
|---|---|---|---|---|
| Sigmera (this tool) | No — runs in browser | Yes | Free account | None |
| Other online cleaners | Usually yes | Often no | Often | Low |
| Excel / Google Sheets | No | Yes | No | Medium (menus) |
| Python / pandas | No | Yes | No | High (code) |
How to remove duplicates from a CSV
- 1. Open the duplicate remover in your free workspace. Your file is read into the browser’s memory — it is never sent over the network.
- 2. Choose how to match. Keep the first or last copy of each duplicate, and optionally ignore letter case and surrounding spaces so “Ada Lovelace” and “ada lovelace” count as the same.
- 3. Preview the result. See how many duplicate rows were removed and check the cleaned data before you commit.
- 4. Download the clean file. Create a free account to export the full deduplicated CSV.
Why clean duplicates client-side?
Contact lists, sales exports, and sign-up sheets accumulate duplicate rows that inflate counts and break CRM imports. Most online tools fix this by uploading your file to a server you can’t see. Because Sigmera processes the file locally with the browser’s built-in JavaScript engine, there is no server to upload to and nothing is stored — which satisfies GDPR data-minimization (Article 5) because zero bytes leave the device.
Frequently asked questions
- Does this tool upload my CSV file?
- No. The duplicate remover runs entirely inside your web browser using client-side JavaScript. Your file is never uploaded to a server and never leaves your device, so it is GDPR-safe by design.
- How does it decide which rows are duplicates?
- By default it compares the entire row. You can choose to ignore letter case and extra spacing, and keep either the first or the last copy of each duplicate group. Matching on specific columns is being added next.
- Is there a row limit?
- Create a free account — no credit card — to use the tool and download the cleaned file. Rows per file are unlimited on every plan; the Free plan includes 3 downloads a month (Pro 30, Max unlimited), and everything still runs in your browser.
- Can I do this in Excel instead?
- Yes — Excel has a Remove Duplicates button under the Data tab, and Google Sheets has a Data → Data cleanup option. They work, but require opening the file, finding the menu, and selecting columns. Sigmera does it in two clicks without a spreadsheet app.