Always enable whitespace trimming for data from spreadsheets
Spreadsheet exports almost always include trailing spaces in cell values, especially from Excel. These are invisible but cause duplicates to not be detected. Always enable the "Trim whitespace" option when cleaning data that came from a spreadsheet, database export, or CSV file.
Use case-insensitive mode for email lists
Email addresses are case-insensitive by RFC standard — alice@example.com and Alice@example.com are the same address. Always enable case-insensitive deduplication for email lists. Without it, identical addresses with different capitalisation will both remain, causing duplicate sends.
Combine with the word counter to verify list size
After deduplicating, the stats panel shows your output line count. But if you need to verify the result further — check for specific duplicates, count frequency of values — paste the cleaned list into the Word Counter and use the top words panel to spot any near-duplicates you might have missed.
Multi-column data: extract one column first
The tool works on one item per line. If your data is multi-column (CSV or tab-separated), extract just the column you want to deduplicate first. In a spreadsheet, copy just that column. In a text editor, use find-and-replace to extract the relevant values. Then paste into the deduplicator.
Sort before deduplication for reproducible results
By default, the tool keeps the first occurrence of each duplicate. If you care about which duplicate is kept (for example, keeping the alphabetically first version rather than whichever appeared first in the original list), enable sorting before running. The sorted order means the "first occurrence" will consistently be the alphabetically earliest value.
Use numbered output for requirement or feature lists
When producing a cleaned list of requirements, features, or action items, enable line numbering. The numbered output is immediately ready to paste into a document or ticket system, and the numbers make it easy to reference specific items in discussion or review.