Does splitting by vendor create a new order or invoice?

No. It's the same order and the same invoice — only the fulfillment is divided. Totals, payment status and inventory don't change.

Does SplitFlow send the order to my supplier?

It can. Add the supplier on SplitFlow's Suppliers page, and every order with its items is emailed to it with a private link, where the supplier adds the tracking number and marks its items as shipped.

Does it work with a third-party fulfillment service?

It works on fulfillments from your own (merchant-managed) locations. Orders handled by a third-party fulfillment service app are left alone.

How to automatically split Shopify orders by vendor

Dropshipping and multi-vendor stores sell items that ship from different suppliers. When one order mixes them, each supplier's items need their own fulfillment, or someone ends up separating them by hand.

Short answer: Shopify only splits at checkout when products ship from different locations or shipping profiles — and then the customer sees, and pays for, separate shipments. To keep one simple checkout and still separate each vendor's items afterwards, split the fulfillment by vendor: by hand, or automatically with a rule.

Watch: a vendor rule ships a supplier's items in their own shipment (28 seconds).

Option 1: separate shipments at checkout (built into Shopify)

If each supplier's products are stocked at their own location, or sit in their own shipping profile, Shopify's checkout can split the cart into several shipments and the customer chooses a shipping option for each one. That's the right choice when you want to charge shipping per supplier. It's not what you want if customers should see one shipment and one shipping price.

Option 2: split one order by hand

In your Shopify admin, go to Orders and open the order.
In the Unfulfilled section, open the ⋯ menu and click Split fulfillment.
Choose the items (and quantities) that should go into the new fulfillment, then click Split fulfillment.

This works on the desktop admin or Shopify on the web, not in the Shopify mobile app. If you split by mistake, the same menu has Merge fulfillment to put items from the same location back together.

Option 3: split every order automatically by vendor

Install SplitFlow from the Shopify App Store.
Create a rule of type Separate matching items — or click the Dropship supplier preset.
Set the condition to Vendor equals your supplier's name, exactly as it appears on your products.
Click Preview latest order to check it, then save.

Every new order containing that vendor's items now gets them in their own fulfillment order, usually within a minute. Several suppliers? Add one rule per vendor. Rules can also match on product type, product tag, collection, SKU or a metafield, and you can combine conditions with AND.

If a rule never matches, the vendor name probably differs slightly from Shopify's (spelling, spaces, punctuation). The app then shows the vendor names it actually sees in your recent orders, so you can copy the exact one.

After the split

The split is the same order, with its items divided into separate fulfillments. Shopify Flow has a Fulfillment order split trigger, so you can start a workflow whenever an order is split — for example, to put one of the fulfillments on hold or submit a fulfillment request.

Questions

Does splitting by vendor create a new order or invoice?: No. It's the same order and the same invoice — only the fulfillment is divided. Totals, payment status and inventory don't change.
Does SplitFlow send the order to my supplier?: It can. Add the supplier on SplitFlow's Suppliers page, and every order with its items is emailed to it with a private link, where the supplier adds the tracking number and marks its items as shipped.
Does it work with a third-party fulfillment service?: It works on fulfillments from your own (merchant-managed) locations. Orders handled by a third-party fulfillment service app are left alone.