Short answer: It depends which of three different things you mean by “split” — and for the one most people actually mean, the answer is no.
ShipStation has Split Ship (manual), Auto-Split (automatic, but based on product attributes), and multi-package shipments (one shipment, several boxes). These get used interchangeably in conversation and they are not the same feature, don’t run at the same time, and don’t solve the same problem.
None of them answers the question people are really asking, which is: this order doesn’t fit in one box — figure out the cheapest way to divide it. That’s a packing calculation, and ShipStation doesn’t do packing calculations.
Here’s the actual map.
Split Ship divides one order into multiple shipments, each with its own shipment details, tags, notes, packing slip, and customer notification emails. Each gets its own label and its own tracking number. In the orders grid they show as (1 of 2), (2 of 2), and so on.
It’s a manual action — Other Actions → Show Split Ship Actions from the grid, or Split Ship from the order detail screen. You move items into shipments and save. Only orders in Awaiting Shipment can be split.
Two consequences that catch people out, both documented by ShipStation:
There’s a related option — Create Shipment from the Shipments panel — for when you need an extra label but don’t need items associated with it. That’s the tool for “this one line item needs two boxes.”
This is the one that sounds like the answer and isn’t.
Auto-Split automatically creates multiple shipments based on which products are in the order. You configure the behavior per product, in Product Details → Shipping tab. Three options:
It’s plan-gated: High Volume for US, Canada, and ANZ accounts, Enterprise for UK/EU, or an add-on. It doesn’t apply to manual orders. And it runs first — before Preset Groups, Product Defaults, Service Mapping, and Automation Rules. ShipStation also notes that new updates from stores won’t apply to orders after Auto-Split has run.
Read the three options again and notice what’s common to all of them: the split is a property you declared on the product, in advance. “This mattress ships alone.” “These ship 6 to a shipment.” Auto-Split executes a decision you already made. It doesn’t make one.
That’s genuinely useful for the cases it’s designed for — an oversized item, products from different warehouses, a SKU with unique handling. It is not a packing algorithm and doesn’t claim to be.
Different thing entirely. A multi-package shipment is a single shipment containing multiple packages, moving under one master tracking number with the carrier. Split Ship produces separate shipments with separate tracking. Multi-package produces one shipment with several boxes.
Which you want depends on the carrier and the customer experience. Multi-package is how UPS and FedEx handle a genuine multi-piece consignment. USPS doesn’t support multi-carton shipments the same way, which is why heavy USPS orders end up as separate shipments instead.
And here’s the gap: you can’t automate the creation of multi-package shipments in ShipStation. There’s no automation rule action that says “this order needs 4 boxes, build them.” ShipStation support has confirmed this isn’t supported in community threads, and it’s been an open request for years — with the recurring workaround being to import one package via batch and then hand-add the rest, order by order.
If you’re a furniture brand, a coffee roaster shipping 40 lb orders, or anyone whose product ships in ready-to-ship cartons, this is the wall you’ve hit. You know exactly how many boxes each order needs. You just have no way to tell ShipStation to build them.
Line the three up and the shape of the gap is clear.
| Automatic? | Decides how to split? | Based on what? | |
|---|---|---|---|
| Split Ship | No | No — you do | Your judgment, per order |
| Auto-Split | Yes | No — you did, in advance | Product attribute you set |
| Multi-package | No | No | Your judgment, per order |
Nothing in that table takes an order, looks at what’s in it, and works out the split.
To answer “what’s the cheapest way to divide this order into boxes,” a system has to:
Steps 1 through 4 are all things ShipStation’s automation layer structurally cannot do. The rules engine can’t read multiple line items, can’t do arithmetic, and can’t call out for external data. Auto-Split runs before any of that anyway, off a product flag. And rating happens downstream of packing, which is the same reason flat-rate programs can’t be rate-shopped properly.
None of this is ShipStation being deficient. Cartonization is a genuinely hard computational problem, and building it means knowing the dimensions of every SKU in a catalog it doesn’t own. It’s not a reasonable thing to ask of a horizontal platform serving 130,000 businesses.
Tag it and alert. The documented ShipStation pattern: use automation rules to identify orders that need splitting and add a tag plus an alert, so a human knows to handle it. Doesn’t split anything, but stops orders slipping through. If you’re doing 20 of these a day, this is a fine answer and you should stop reading.
Product-level Auto-Split. If your split rule really is a product property — “the 25 lb bag always ships alone” — Auto-Split is exactly right. Configure it and move on.
Assumptive quantity rules. Rules like “if quantity is 3, use the 3-box configuration.” Works if you sell one product in one size. Falls apart the moment orders mix SKUs — and the multi-item orders are the ones that need splitting most, and the ones SKU-based criteria skip entirely.
Batch import one package, add the rest by hand. The community workaround. It works. It’s also 300 orders × a manual step, every day.
A layer that does the calculation. Something above ShipStation that reads the full order, solves the fit against your real boxes, prices the candidate splits, and writes the result back before your warehouse sees the order.
That last one is what String does. We know your SKU dimensions and your packaging, we solve the fit, and we work out the most cost-effective way to split an order across boxes based on your actual carrier rates — then the order lands in ShipStation already configured. Your team packs what the screen says and prints.
If you’re currently hand-building multi-package shipments, tell us what your orders look like and we’ll tell you what it’d take — including if the answer is that Auto-Split already covers you and you don’t need us.
What’s the difference between Split Ship and a multi-package shipment in ShipStation? Split Ship divides an order into separate shipments, each with its own tracking number, packing slip, and customer notification. A multi-package shipment is one shipment containing several boxes under a single master tracking number. Split Ship is for “these items ship separately.” Multi-package is for “this shipment is four boxes.”
Can ShipStation automatically create multi-package shipments? No. There’s no automation rule action to build multiple packages on a shipment. ShipStation support has confirmed this isn’t supported. The common workaround is batch-importing one package and adding the rest manually per order.
Does ShipStation Auto-Split decide how to split an order? No. Auto-Split executes a rule you configured on the product record — ships individually, exclusive bulk, or a custom quantity per shipment. It doesn’t evaluate what’s in the order or work out a split. It’s plan-gated and runs before all other automation.
Can an automation rule split an order by weight? Not into packages. You can use weight criteria to tag an order and raise an alert so someone handles it manually, but no rule action divides an order into multiple boxes.
Why doesn’t my SKU-based split rule fire on multi-item orders? Because Item SKU, Item Name, and Warehouse Location criteria only evaluate single-line-item orders. Use product tags instead — though tags tell you a product is present, not how many there are.
Do split orders still update from my marketplace? No. ShipStation documents that orders containing split shipments are no longer updated with changes from the selling channel. Self-service Branded Returns also stop working for split orders.
Is it cheaper to ship two boxes or one big one? Often two, once dimensional weight is in play — a single oversized carton can price above two smaller ones on the same total weight. It depends on your carrier, your zones, and your actual box dimensions, which is exactly why it’s a calculation and not a rule of thumb.
Most ShipStation stores are — oversized boxes, rate programs that never get checked, and packaging that doesn't match what's actually being shipped.
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