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Getting Started

This guide will walk you through installing Rate Lab and creating your first custom shipping rate.

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Install Rate Lab

  1. Find Rate Lab in the Shopify App Store Visit the Shopify App Store and search for “Rate Lab” or use your direct installation link.
  2. Install to your store Click “Add app” and follow the prompts to authorize Rate Lab to access your store’s shipping settings.
  3. Open Rate Lab After installation, find Rate Lab in your Shopify admin under Apps. Click to open the Rate Lab workspace.

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Your first custom rate

When you open Rate Lab, you’ll see three panels filled with a working example. Let’s understand what you’re looking at:

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Left panel: Your Liquid template

This is where you write your shipping logic. The default example shows a simple rate calculation: 
{% liquid
  assign service_name = "Rate Lab Test"
  assign total_weight = shopify_rate_check.line_items | sum: "grams"
  assign weight_price = total_weight | divided_by: 1.5 | round
%}
{
  "rates": [{
    "service_name": {{ service_name | json }},
    "service_code": "RL",
    "currency": "USD",
    "total_price": {{ weight_price }}
  }]
}
This calculates shipping based on the total weight of items in the cart.

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Top right panel: Order data (Context)

This shows what information Shopify provides about the order - items, quantities, destination, cart totals, etc. Your Liquid template uses this data to calculate rates.

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Bottom right panel: Rate results

This shows the shipping rates your template produces - what customers will see at checkout.

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Try modifying the rate

Let’s make a simple change:
  1. In the left panel, find this line: 
    assign weight_price = total_weight | divided_by: 1.5 | round
  2. Change it to charge more per gram: 
    assign weight_price = total_weight | divided_by: 1.0 | round
  3. Click the Run button at the top
  4. Watch the bottom right panel update to show the new shipping price
That’s it! You’ve just modified your first shipping rate calculation.

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What’s actually happening?

When a customer reaches checkout, Shopify sends order information to Rate Lab. Your Liquid template processes that information and returns shipping rates. The customer sees these rates as options at checkout. The three-panel interface lets you test your logic safely before customers see it. You can:
  • Edit your Liquid template (left panel)
  • Test with different order scenarios (top right panel)
  • See the resulting rates immediately (bottom right panel)

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Next steps

Now that you understand the basics, learn more about: