JsRates

What JsRates is

JsRates is a custom shipping rate tool for Shopify merchants. It lets you write shipping logic in JavaScript, call third-party APIs, and test rules before they affect checkout, which suits rates that depend on region, weight, product mix, customer type or external data.

What you can do with it

• Write shipping rules in JavaScript
• Pull warehouse, logistics or membership data through APIs
• Test rules against real carts
• Charge different rates by customer group

Who it is for

• Shopify merchants with complex shipping
• E-commerce teams using external rate data
• Developers configuring store checkout

What to watch out for

• Wrong shipping logic directly affects orders and revenue; test boundary cases and API failures
• Checkout performance matters, since rate calculation runs during purchase
• Free request allowances and paid plans should be confirmed
• Avoid sending customer personal data to third-party APIs without a lawful basis