1. Scan Capacity
Engine analyzes SKU dimensions against the active shipment box.
v4.0 Shipping Engine
For frozen and refrigerated orders, shipping is expensive. Fits In The Box shows what customers can still add without moving to the next shipping tier.
Implementation
Engine analyzes SKU dimensions against the active shipment box.
Show add-ons that still fit and keep shipping unchanged.
Update cart messaging in real time as customers top up orders.
Show only add-ons that fit the active shipment so customers can top up without shipping surprises.
Live Checkout Logic
Upsell Intelligence
Fits!0.2 ft³Honey & Spreads
Fits!0.1 ft³Nut Butters
Fits!0.5 ft³Crackers & Snacks
Built for the modern Shopify merchant
For frozen and refrigerated orders, shipping is expensive. Fits In The Box shows what customers can still add without moving to the next shipping tier.
Live widget

at checkout
Operational checkout signalShipping-tier protection
Smart volumetric engine
Real-time fitting logic runs on every cart update.
Only products that do not increase shipping are shown.
Messaging stays consistent as customers add products.

Honey & Spreads

Nut Butters
POPULARJoin merchants reducing high-cost frozen and refrigerated shipping by filling each box more efficiently.
Install on ShopifyDeep Dives
See how packing-aware recommendations help cold-chain stores fill paid shipping capacity before checkout.
Explore the use caseUse the packing engine in custom storefronts, middleware, warehouse workflows, or checkout logic.
Read the API docsFollow the install path for boxes, product dimensions, theme extension setup, and first widget launch.
Open the tutorial