Shopify Amazon integration that keeps one stock count

Marketplace Connect is Shopify’s free option for connecting your store to Amazon. Shopify builds it, it used to be called Codisto, and it runs from inside the Shopify admin. If Amazon is the only other place you sell, try it first. We would rather you did than paid us to find out the same thing.

It is built around Shopify: your listings, stock and orders live in the Shopify admin and Amazon hangs off it as a channel. That works until something which is not Shopify also holds stock: a Square till, an Etsy shop, a count in QuickBooks. Two channel apps plugged into Shopify have no way to tell each other anything.

One extra channel? Marketplace Connect is likely enough. Several places selling the same physical item? You need one count in the middle that belongs to none of them. That is what QuickSync is, and why we are not trying to be a cheaper Marketplace Connect.

Shopify holds a SKU of up to 255 characters. Amazon takes 20. The SKU is what identifies an item on both sides, so a truncated one stops matching what it came from. That is the most common reason a sync looks connected and still moves the wrong numbers.

WINTER-JACKET-NAVY-XL is 21 characters → Amazon truncates it to WINTER-JACKET-NAVY-X → the SKU no longer matches. We truncate rather than refuse to send, so nothing errors and nothing turns red: the item quietly stops pairing with itself and you find out when a count drifts.

Check your longest SKUs before you connect. Shortening a pattern once at the start costs far less than reconciling two counts later, and it is worth doing whichever tool you use: the 20-character limit is Amazon’s, not ours.

We send your stock figure to Amazon whatever the fulfilment method, so a sale on Shopify lowers what Amazon shows either way. What changes is the direction coming back. For FBM items (the ones you pick and post yourself), we hear about Amazon-side changes and pass them to Shopify. For FBA items, which Amazon holds and ships, we leave the count alone on purpose.

That is deliberate rather than unfinished. Amazon owns the stock in its own warehouses and knows those shelves better than we do; writing our number over theirs would mean guessing at receipts, damages and returns that never pass through us.

Amazon also has no way for us to send a tracking number back, so if you ship an Amazon order from stock you sell elsewhere the tracking stays in QuickSync and in the shop the order came from.

In short: FBM stock syncs both ways. FBA stock stays managed by Amazon.