Bring contacts you already have

LinkedIn lets you download your connections as a CSV. Contacts → Import takes that file directly, including the preamble rows LinkedIn puts above the header. It matches columns for you and shows what it guessed before importing anything.

People are matched on their LinkedIn URL, so re-importing an updated file adds nothing the second time. Rows without a URL cannot be matched and always create a new person — so importing the same file twice without URLs will duplicate. Contacts → Duplicates finds those afterwards.

This is also the honest answer to updating many people at once. A fresh LinkedIn export re-imported here brings every changed employer in one step, without a single page being read.

For somebody you met away from LinkedIn, Contacts → Add manually takes a single row through exactly the same path, so deduplication and company matching behave identically.