The id attribute in Google Shopping feeds

The id is each item's permanent identity in Merchant Center. Google keys approval status, quality history and performance data to it. The cap is 50 characters. Changing an id later deletes that history and puts the item through review again as a brand new offer.

How this app fills it

• The default format combines your product and variant ids in the same shape Shopify's own channel uses, so switching apps keeps item history.
• The Basic tab offers other formats. Product and variant ids, the bare variant id, or your SKU.
• The id can never be overridden per product. It is how Google identifies each item.

Dos

• Pick an id format once, before you register the feed, and keep it forever.
• Match the format your previous feed used when migrating from another app. History carries over.
• Use SKUs only if every variant has one and they never get reused.

Don'ts

• Never change the id format on a live feed. Every item is treated as new and re-reviewed.
• Don't reuse an id for a different product. Google attaches the old history to the new item.
• Don't put changeable data like price or stock in an id.