This tutorial assumes you are familiar with the Checkout SDK. If you are unfamiliar with the Checkout SDK, refer to Getting Started with Checkout SDK to get some general information.
In this tutorial, we will create a custom checkout using a checkout loader file, building on the steps from the Getting Started with Checkout SDK article. This tutorial will outline how to package a custom checkout file and install a custom checkout using the control panel.
In your text editor, create a file for upload called checkout-loader-<version>.js with the following content, where <version> represents an arbitrary version number used for invalidating cached versions of the file.
Comparing the content of this newly created file and the code from the Getting Started with Checkout SDK, you should see a clear resemblance between the two.
You can upload the checkout-loader.js file to your store’s server using WebDAV by following the instructions below:
/content folder, create a new folder, and name it checkout.checkout-loader.js into the newly created checkout folder on WebDAV.To install a custom checkout on a store, follow these steps:
NOTES:
Prepending webdav: indicates that the URL is in the remote WebDAV directory. It treats /content as the root WebDAV directory.
It is best practice to include a <version> number in the Script URL field. Note that if you change the same provided loader filename, you could serve a cached version to the user.

In the developer console, you will see the checkout object, and you can test out additional state.data commands.
This tutorial also gives you the steps to build a custom checkout. Instead of working with code in our theme, as shown in the Getting Started with Checkout SDK article, we created a file and uploaded it to WebDAV, effectively taking over the entire checkout experience.
Sample apps