Google cart transfer (Universal Cart)

Google cart transfer lets Google hand a shopper's cart to your store. A shopper builds a basket in Google (Search or Gemini, in Google's Universal Cart), and when they choose to buy, Google sends the items and quantities to Brainerce. Brainerce builds a cart in your store and sends the shopper to your cart page with those items already in it. They check out in your store, with your shipping, taxes and payment methods, like any other customer.

Read the next section before you start. It answers most of what merchants expect that this does not do.

What it does not do

• Nobody pays inside Google or Gemini. The shopper always finishes on your store's checkout. Google never takes a payment for you, never creates an order, and never receives card details. This applies to every step below.
• It does not make your products appear in Google. Turning it on only lets Google send a cart to you. Whether your products show up in Google's cart at all is Google's decision, and it depends on your products being in Google Merchant Center. Brainerce cannot guarantee it, speed it up, or see it.
• Google approves each store. Google reviews the integration for your store in Merchant Center. Brainerce cannot grant that approval. Until Google approves, the setup on this page can be complete and nothing will arrive.
• Only a cart is handed over. Google sends the items and the quantities. It does not send the shopper's name, address, email or phone, and Brainerce does not read or store any buyer details from the request. The shopper enters their details at your checkout. They do not need to be logged in.
• The price in Google's cart is an estimate. Tax and shipping are worked out at your checkout, and the total Google shows says so.
• Stock is not held. The cart does not reserve inventory for the shopper. An item can still sell out before they pay.
• It is not an order channel in your reports. Orders that come this way are ordinary orders from your storefront. Brainerce does not yet report them as a separate channel.

What you need before you turn it on

1. A sales channel with a storefront address. Add it in the sales channel settings. Google finds your profile on your own domain, so without an address nothing can work.
2. A storefront that serves the Google profile page. This is a small page at /.well-known/ucp on your own domain. Brainerce cannot add it to a store that is already built, and upgrading Brainerce does not add it either. A store made with the current Brainerce template has it, or will once the template carrying it is released. A store built earlier, or by hand, needs it added by whoever built the store. They can use the developer reference. If you are not sure, run the checks below: one of them tells you.
3. Your products in Google Merchant Center. Cart transfer only works for products Google already knows about, and the ids those products have in Merchant Center must match the product ids in Brainerce, or Brainerce cannot tell which product Google means. The Product ids check on the card compares them. See Get found on Google.
4. A store whose currency matches what Google shows. Carts are always priced in your store's currency. Brainerce does not convert them. If Google shows your products in a different currency, a check will fail and tell you.

Turn it on

1. Open Apps → Google, pick your sales channel, and open the Merchant Center tab.
2. Find the Google cart transfer card. If you have not connected Google yet, it appears on the Settings tab instead, because the other tabs need a connected channel.
3. Switch Allow Google to send carts to this channel on. Turning it on only starts serving your profile to Google. It does not create a key and does not send anything to Google yet.
4. The card then offers Create sandbox key as the next step.

Switching it off stops your store from serving the profile and stops Google from sending carts to this channel. Your keys stay on file, but they have nothing to open while it is off.

Create the key and send it to Google

Google asks for a key by email so that only Google can send carts to your store. There are two:

• Sandbox key. For testing in Merchant Center. It works while the sales channel is in test mode or live mode.
• Production key. For real shoppers. It works only while the sales channel is live. Create it when you are ready to go live.

To create one, press Create key on its row. The key appears in a window once. Copy it right away, because it cannot be shown again. If you close the window without copying it, replace the key and copy the new one. After that the row shows only the start of the key, when it was created, and when it was last used (or Never used), which is how you can tell whether Google has started calling.

Then send the key to Google by email. The email address is in Merchant Center, under UCP integration. Brainerce does not send it for you, and nobody at Brainerce can read it back to you.

Keep the key private. Anyone who has it can create carts in your store through Google's route. Share it only with Google. Brainerce's AI assistant and the connected AI tools never create, replace or show a key, on purpose, so a key never ends up in a chat.

Replace a key

Press Replace key on the row. A new key is created and shown once. The old key keeps working for 24 hours, so you have time to send the new one to Google. After that the old one stops. Google swaps keys by hand, so allow for it.

Revoke a key

Press Revoke key. Requests that use it stop working right away, with no grace period. You can create a new key at any time.

Add the integration in Merchant Center

In Google Merchant Center, find UCP integration in the settings and add the integration for cart only. Give Google your profile address, which the card shows under Profile address on your store, and send the key as described above.

Select only the cart. Brainerce's profile declares the cart and nothing else, and what you choose in Merchant Center has to match it. Brainerce cannot see what you selected there, so this match is yours to check.

Google runs its own test and review of the integration. How long that takes, and what it needs, is Google's process: Brainerce cannot see it or hurry it.

Run the checks

On the card, press Run checks. Brainerce looks at your real storefront and builds a real test cart, which it deletes straight away. It tells you how many checks passed and names the ones that need attention. The same checks, with details, are on the Readiness tab. See The Google Readiness tab.

A passing run means Brainerce's side is ready. It does not mean Google has approved the store or that products will appear.

What the checks mean, in plain words:

• Storefront address. The channel needs an address on your own domain.
• Sandbox key. You have created one.
• Sales channel live. A production key only works while the channel is live. A test with the sandbox key does not need this.
• Address Google calls. The server address that your profile gives Google must be a public https address. If this fails, it is a Brainerce setup problem: contact support.
• Profile on your store. Your store must answer at /.well-known/ucp. A "404" means the page is missing: either cart transfer is switched off or has no address (the check says which), or your store was built without the page and needs it added. A redirect also fails, because Google does not follow one: both the www and the bare version of your address must answer directly.
• Profile content. The page must be served as JSON, kept for at least 60 seconds, and point to the right server address.
• Profile matches. The page your store serves must be exactly the one Brainerce builds. Do not edit it.
• Test cart. Needs at least one published product that is in stock.
• Currency. The currency Google sees must equal your store currency.
• Product ids and prices. Warnings. Google can name a product in two ways, and both should lead to the same product. The price in the cart should match the price in your product feed. A price set only for one sales channel is the usual reason they differ.

What the shopper sees

The shopper lands on your cart page with the items already in it. They continue to your checkout from there.

• A product that needs a choice is not added. A product with required options or customisation fields, or a product with variants where Google did not name one, cannot be added through Google. Google is told the item could not be added.
• An item that is out of stock is left out, not reduced. If you have fewer units than the shopper asked for, that line is not added at all, and Google is told how many are available.
• Some items can go in while others do not. The cart holds what can be sold. If nothing can be sold, the shopper lands on your home page.
• The cart lasts 24 hours (one hour for a test with the sandbox key). A cart nobody opens is deleted.

Limits

• A request from Google can list up to 100 lines. A cart holds up to 50 different items, and up to 100 of one item.
• Each key can make 300 calls a minute, and one sales channel can create 2000 carts an hour. These are there so that a leaked key cannot flood your store.

Common questions

Why does it say Google's cart total is "estimated"?

Because tax and shipping depend on the address and the delivery method, which the shopper chooses at your checkout. The final total is the one in your checkout.

Can shoppers pay in Google or Gemini?

No. Nobody pays inside Google or Gemini through this feature. The shopper always pays in your store.

Will my products now appear in Google's cart?

Not necessarily. Turning this on lets Google send a cart to you. Whether your products appear is up to Google, and Brainerce cannot guarantee it.

I turned it on and nothing arrives. What now?

Run the checks on the card and fix the ones that fail. If Google names a product that Brainerce does not recognise, that item is left out of the cart: the product ids in Merchant Center must match the product ids in Brainerce. If the checks all pass, the next step is Google's review of your integration in Merchant Center. Brainerce cannot see its status.

Can the AI assistant create the key for me?

No. A key is a secret, so it is only ever created and shown in the dashboard, to you.

Does it work for a store connected by store id instead of a sales channel?

No. Cart transfer belongs to a sales channel.

What's next?

• Get found on Google: getting your products into Google Merchant Center, which cart transfer relies on.
• The Google Readiness tab: every Google check in one place.
• A feature you turned on is not showing on your website: what to do when your store was built before a feature existed.