# Will re-importing the same CSV create duplicate leads?

No. CSV imports, which your LeadAttractor team runs for you, match on the phone number, and the Lead API does too, so pushing the same lead twice updates it rather than duplicating it.

Because matching happens on the phone number, if you see duplicates after an import, check that the phone column was mapped correctly. Row-by-row validation also reports which rows failed and why, so a few bad rows do not fail the whole file.

Read online: https://docs.closemagnet.com/articles/questions/reimport-csv-duplicates