Uploading a spreadsheet to create or update products in bulk.
Shopify's Products → Import accepts a CSV whose column headers match the documented product export schema. Rows update matching handles or create new ones. It is the fastest way to migrate a catalog and the fastest way to destroy one: blanks are treated as blanks (a missing SEO title empties the SEO title), variant rows must appear immediately after their parent product, and there is no preview and no undo. Always export first, edit the export, and keep the original as a snapshot.
