For ShipStation sellers with multi-item orders

Stop picking a box for every order.

ShipExtension sizes the box for every order in the batch and writes it back to ShipStation. It can also rate shop and print the batch's packing slips.

You keep ShipStation, your carriers, and your rates.

  • The smallest box on your list that fits, worked out in 3D
  • Dimensions written back to ShipStation, so DIM weight and rates are right
  • Rate shopping and retailer packing slips when you want them
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A D B C E

12" × 8" × 6"

Medium Box

Five SKUs, one order, one carton. Picked before the warehouse sees it.

Getting started

Start with one job you repeat every day

  1. Tell us the task.
  2. We set up the workflow and show you a preview on your own orders.
  3. You approve it. Then it runs.

If ShipStation can already do it on its own, we'll tell you.

Built inside the founder's own operation: four years of D2C, marketplace, and big-box drop-ship orders at 1,000–2,000 a day. Read the case study

1,000–2,000
orders processed per day
3–4 hrs
of daily prep work removed
4 yrs
running 1,000–2,000 big-box orders a day

Sound familiar?

The parts ShipStation leaves to you

At a few hundred orders a day, you already know where the hours go.

4–5 hours a day of the same decisions

Picking a box for every multi-item order. Rate shopping one shipment at a time. Sorting batches by carrier.

Packing slips from a portal, not your printer

Slips downloaded from Rithum or SPS Commerce don't print with your labels. Split shipments mean editing PDFs by hand.

Scripts held together with tape

Weather checks, UPC matching, and the exceptions that always land on the same person.

How it works

Connect once, then every sync runs your rules

No migration. No new carriers.

1

Connect ShipStation

Paste your API keys. Five minutes, nothing to install.

2

Build your rules, or we do it

Start with one task you repeat. We'll set it up with you and show you a preview first.

3

Orders arrive ready

Every sync runs your rules on the whole batch. You open ShipStation and the orders are boxed and rated.

What's in it

Six jobs you stop doing by hand

Retailer-Compliant Packing Slips

Generated from the ShipStation order and printed in line with your labels. Split shipments list only what's in the box. Home Depot, Macy's, Lowe's, and Bloomingdale's formats.

Automation Rules

Rules that see the whole order: several SKUs at once, the channel, the weather. Applied before anyone touches it. No code.

Box Optimization

3D bin-packing picks the smallest box that fits, multi-item orders included.

Rate Shopping

Every shipment checked across all your carrier accounts. The cheapest service that qualifies wins.

Chrome Extension

Run your rules and see the packing result inside ShipStation's own screens.

Integrations

Zapier, n8n, and weather data, so a rule can react to more than what's on the order.

Before vs after

What changes day to day

Before ShipExtension

  • Someone picks a box for every order
  • Slips downloaded from vendor portals and matched to labels by hand, plus PDF surgery for every split shipment
  • Oversized boxes and rates nobody checked
  • A backlog every peak season

After ShipExtension

  • The box is picked by 3D bin-packing
  • Slips generated from the ShipStation order and printed with the label, split shipments showing only what's in the box
  • Right-sized boxes and rate-shopped carriers on every shipment
  • A log of which rules ran and what they changed

Who it's for

Who it's for, and who it isn't

This is for complex, high-volume shipping. If that isn't you, it won't pay for itself.

A good fit if

  • You ship 1,000+ orders a month
  • You have a lot of SKUs, or orders that put several items in one box
  • You use more than one box size, or more than one carrier account
  • You ship for big-box drop-ship programs (Home Depot, Macy's, Lowe's)
  • You ship perishable, fragile, oversized, or special-handling products
  • Your team keeps scripts, spreadsheets, or a big stack of automation rules alive
  • You're a 3PL running client stores under one ShipStation account

Probably not if

  • You're low volume, with mostly single-SKU orders
  • You ship in one box with one carrier
  • ShipStation's own Rate Shopper does what you need
  • What you're really shopping for is inventory or warehouse management

FAQ

Questions we get

Will this mess up my existing ShipStation setup?
No. It reads your orders over the API and writes back only the fields your rules touch. Your ShipStation configuration stays as it is.
Can you set it up for me?
Yes. We build the rules and packing slip templates with you, retailer formats included if you ship for drop-ship programs, and hand you a working setup.
Do I need to migrate data or change carriers?
No. You keep your carriers, boxes, negotiated rates, and everything you've already configured.
What if I process orders in large batches?
That's what it's built for. Orders sync in batches and every rule runs across the whole batch.
Do I need to be in a big-box drop-ship program to use this?
No. Box selection, rate shopping, and rules work for any ShipStation seller. Retailer packing slips are an add-on for the sellers who need them.
Is my ShipStation data secure?
API keys are encrypted at rest with AES-256. We sync only the order data your rules need and never sell or share it. Read the security overview →
Doesn't ShipStation already have automation rules?
Yes, and keep using them. Native SKU conditions only fire on single-item orders. ShipStation's Packing Recommendations beta will suggest a box, one order at a time, when you open the order. ShipExtension handles the multi-SKU rules and picks the box for the whole batch without anyone opening anything.
Does rate shopping use my negotiated carrier rates?
Yes. Rates come from the carrier accounts already connected to your ShipStation. All of them are compared, and the winning carrier, service, and billing account are written back.
Will it conflict with my existing ShipStation automation rules?
It shouldn't. Native rules run once, at import. ShipExtension runs after that, on the synced order, and only touches the fields your rules target. A value that's already right is never rewritten. Preview it on your own orders first.
Where do product dimensions for box optimization come from?
From your ShipStation product records. We sync each SKU's dimensions and weight, and you can override any product in ShipExtension. An item with no dimensions is left out of the box calculation and flagged, so measure your catalog before you turn this on.
How do packing slips print?
Pick a batch. We build one PDF, slips only or slips interleaved with your labels, so each order's paperwork comes off the printer together. Retailer templates or your own design. Download it and print in one job.
What happens at high volume or ShipStation API rate limits?
Orders are processed as they sync, so there's no big batch waiting. Every API call watches ShipStation's rate-limit headers and paces itself; if a limit is hit we wait it out and retry. Writes go out 50 orders at a time and unchanged values are skipped. A 500-order rate-shopped run usually finishes in 20 to 40 minutes, with live progress in the dashboard.

Heavy user of ShipStation's native rules? See the full comparison

Open ShipStation to orders that are already done

Start a free trial, or get help setting up your first workflow.

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No credit card · Setup help available · Packing slips are an add-on