Excel can handle straightforward duplicates, but it gets weaker when the same contact is represented with slightly different formatting. That is where manual cleanup slows down.
Most duplicate rows in Excel come from copy-paste merges, repeated exports, and sheets that were edited by several people over time. The duplicates are rarely identical all the way across the row.
In contact lists, email is often the best first pass. If the email column is incomplete, phone may be the better fallback. Full-row dedupe helps only when the export contains literal repeats.
If the rows are nearly identical, Excel can get you through it. If formatting drift is hiding matches, manual work becomes slower and easier to get wrong.
Whitespace, casing, and phone punctuation often make one person look like two. Clean those first or use a cleanup flow that does dedupe and normalization together.
Once the repeated contacts are removed, export one clean CSV and use that version for import, outreach, or handoff. Do not keep branching the messy original.