Shopify's product CSV import silently discards variant metafields. Tested on a live store with all three documented header spellings: none of them wrote a value, and every import reported success. Fieldloader exports one metafield to CSV — a row for every variant, including the empty ones you are there to fill in. Edit it, send it back, and see the diff before anything is written: what is new, changed or cleared, and every bad row against its line number. One click puts a whole import back.

• A row for every variant, including the ones with no value yet
• See the diff before anything is written — nothing writes while a row is wrong
• Bad rows reported against their line number, never silently dropped