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What is Rate Lab?

Rate Lab is a Shopify app that gives you complete control over your shipping rates through custom logic. Instead of being limited to basic carrier rates or simple flat fees, you can create sophisticated shipping calculations that respond to your cart contents, destination, products, and business rules.

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What you can do with Rate Lab

Cart-based pricing Charge a percentage of cart subtotal, offer free shipping over a threshold, or adjust rates based on total weight or item count. Product-specific logic Apply surcharges for oversized items, hazmat fees, or special handling. Filter rates based on SKU, vendor, or product properties. Geographic controls Block shipping to PO boxes, charge extra for remote regions, or offer different rates by country, state, or postal code. Multi-vendor operations Calculate separate fees per vendor, cap rates by fulfillment partner, or route orders based on warehouse location. Dynamic rate descriptions Show customers exactly why a rate costs what it does, with contextual messages based on their order.

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How it works

Rate Lab provides a three-panel workspace in your Shopify admin:
  1. Write shipping logic using Liquid templates - the same template language you use in Shopify themes
  2. Test with real order data by previewing exactly what Shopify sends during checkout
  3. See instant results as you make changes, with live updates showing the rates customers will see

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What’s in this guide

Getting Started - Install the app and create your first custom shipping rate Using the IDE - Learn the three-panel interface and how to test your logic Understanding Your Data - See what information is available for your shipping calculations Shipping Logic Examples - Copy and adapt proven templates for common scenarios Reference - Troubleshooting tips and glossary of terms Ready to take control of your shipping rates? Continue to Getting Started.