Replace audience companies

Upload the company rows of a LinkedIn company_list audience (account-based marketing). LinkedIn-only, every other platform returns 422.

A LinkedIn audience segment holds exactly one uploaded list, so the list you send here REPLACES the segment's list instead of being appended to it: always send the full set of companies. LinkedIn returns only the identifier of the uploaded file, never its rows, so the merge cannot be done for you, keep the source list on your side. LinkedIn does not document how quickly companies dropped from the list stop being targeted, so treat removals as eventual rather than immediate. Rows are plain text (not hashed), matched against LinkedIn's own company graph. Matching is asynchronous: LinkedIn takes up to 48h for a new audience and up to 24h for a later update, and the audience stays processing meanwhile. LinkedIn recommends at least 1,000 companies for a usable match rate, and caps a list at 300,000.

The initial list is sent with companies on POST /v1/ads/audiences; this endpoint is for every change after that.