Store Builder

FastSpring's JavaScript library for embedding e-commerce features directly into your website. Power everything from Buy Now buttons to fully branded checkout flows.

What can you do with Store Builder?

These building blocks help you create a seamless, dynamic e-commerce experience.

Directives

Display product and order data using HTML only

Actions

Trigger checkout and cart behavior using HTML attributes

Methods

Control session and checkout logic using JavaScript

Callbacks

Run JavaScript after FastSpring events like add to cart or purchase

Session objects

Prefill customer details and control checkout behavior

Secure payloads

Encrypt sensitive session data like pricing or tax ID

Add Store Builder to your site

Add the following script to any page where you want to use Store Builder:

<script 
    id="fsc-api"
    src="https://sbl.onfastspring.com/sbl/1.0.3/fastspring-builder.min.js"
    type="text/javascript"
    data-storefront="your-storefront-URL">
</script>

Replace your-storefront-URL with the full path to a checkout in your store (e.g., yourstore.test.onfastspring.com/popup-checkout).

Attribute	Description
`id`	Identifies the script block (must be `fsc-api`)
`src`	The script source and Store Builder version to load
`type`	Declares the script as JavaScript
`data-storefront`	The full URL to your FastSpring checkout

Where do I find my checkout URL?
In the FastSpring app, go to Checkouts > Popup Checkouts. Select a checkout and click Place on your website. In the modal that appears, find the URL in the data-storefront line of the script snippet. This is the value you’ll use for data-storefront in your implementation.