Source of truth

Each kind of your data — catalogue, price, stock and who acts on an order — has one system that decides it. One answer per kind, not one for your whole account.

Every piece of your product data has exactly one system that decides it. We call that system the source of truth for that data. Everywhere else receives a copy.

The important part, and the part that surprises people: it is not one answer for your whole account. It is one answer per kind of data.

The diagram above covers the three kinds of product data. There is a fourth, orders, which is about who acts rather than who decides a value — it is described below.

The four kinds

Each can have a different owner, and normally does. A common shape: the catalogue was originally pulled from Etsy, prices are set in MarketplaceHub, stock is pushed in by a warehouse system over the API, and that same system is expected to ship. All four are true at once.

Who can own each kind

• MarketplaceHub — you edit it here and every marketplace receives it. This is what the rest of the product is built around.
• A marketplace — that shop decides, and MarketplaceHub copies the value in.
• A file feed — your scheduled CSV or JSON import sets it. Price and stock only.
• Your own system — an ERP or warehouse pushes it over the API. Price, stock and orders.

Not every kind accepts every owner. The catalogue can be owned by MarketplaceHub or a marketplace. Price and stock accept all four. Orders accept only two — MarketplaceHub or your own system.

Why Amazon and eBay cannot own price or stock

For a marketplace to own price or stock, something has to send changes into MarketplaceHub continuously — not once, but every time a value moves. Two integrations can do that today:

• Shopify sends a webhook the moment a variant changes.
• Etsy has no webhook for stock, so MarketplaceHub polls the shop on a schedule instead.

Amazon and eBay have neither. Naming one of them as your price or stock owner would look like it worked and then quietly do the opposite of what you wanted: MarketplaceHub would start ignoring every other channel's changes on the grounds that they are not the owner, while nothing ever arrived from Amazon to replace them. Your listings would keep whatever figures they last had, indefinitely.

So they are not offered. They can own the catalogue — a content import is a thing all four marketplaces support.

Why no marketplace can own orders

Because it is not a fact about your account. Whether a marketplace ships an order is a fact about that order: one Amazon seller runs FBA and merchant-fulfilled listings side by side in the same account, so there is no answer that is true for all of them. The per-order answer is handled separately, below.

What the orders owner decides

It decides who is expected to ship, cancel and refund — you, working the Orders page, or your own system calling the orders API. Unlike price and stock, nothing about orders runs on its own: every push starts with a person pressing a button or a call arriving, so there is no standing sync to stop when the owner moves.

That is why this owner is advisory. Neither surface is ever blocked:

• If your own system owns orders, the Orders page still ships from here. It tells you first that your system was expected to.
• If MarketplaceHub owns them, an API shipment is still accepted, and the response carries the same notice in its warnings array.

Refusing a deliberate action would be worse than doing it and saying what it contradicts.

One thing is refused, and it is not about ownership. An order the marketplace fulfils itself — an Amazon FBA order — cannot be shipped, cancelled or refunded through MarketplaceHub at all, because Amazon is already doing it. The API refuses it and names each line, checked before anything is written so a bad third item cannot leave the first two already confirmed. Only Amazon reports a fulfilment channel; an order from eBay, Shopify or Etsy is always treated as one you ship yourself.

What "demoted to a target" means

When you move a kind of data away from a marketplace, that marketplace does not get disconnected. It stops being asked and starts being told. Concretely:

• Its incoming sync stops. Etsy's scheduled poll is removed; a Shopify subscription stops being treated as a source.
• It keeps receiving everything. The catalogue, prices and stock still publish to it exactly as before.
• Changes made on that marketplace stop reaching MarketplaceHub. If someone edits a price in the Etsy dashboard after Etsy has been demoted, MarketplaceHub will not learn about it — and will overwrite it on the next publish.
• For the catalogue, only Shopify has an automatic sync to stop: its product webhooks and its 30-minute catch-up pull are ignored once the store is not the owner. The Etsy, eBay and Amazon catalogue pulls are started by you, so nothing is paused for them — a pull you start still runs, and tells you first who owns the catalogue and that it can overwrite edits made in MarketplaceHub.

That last point is the one worth telling your team about before you switch.

Editing something that somebody else owns

Nothing stops you. If you push a price with a feed or over the API while a marketplace owns price, the change is applied — and you are warned: in the import's job log for a feed, in the warnings array of the response for an API call:

Etsy is your price master, so this price will be overwritten the next time Etsy syncs. Change the master on the Data Flow page if you want this value to stay.

Refusing the edit outright would be worse: sometimes overwriting a value for an hour is exactly what you want, and a system that silently declines to do what you asked is harder to work with than one that does it and tells you the consequence.

Seeing and changing it

The Data Flow page in MarketplaceHub shows the current owner of each kind, which way every connection points, and whether an owner was chosen by you or worked out from your settings. That last distinction matters: if you never made a decision, MarketplaceHub infers one from how your syncs are configured, and says so rather than presenting a guess as a fact.

Change on any card walks you through moving that data to a new owner. Before anything is written, the wizard shows you what stops, what starts, and — for price — which SKUs currently disagree and would be changed.

One thing the switch will not do for you

MarketplaceHub does not invent a price it never had. If your products only ever had per-marketplace prices, there is no MarketplaceHub price to fall back on, and the wizard will refuse to make MarketplaceHub the price owner until there is one. It offers to copy the missing prices from a marketplace you choose, which fills the gaps without touching any listing that already has a price.

That refusal is deliberate. A product whose channels disagree has no single correct price, and picking one for you would be a price change nobody asked for.