Add Shopify to existing website - drop down add to cart?

Technical Q&A

Topic summary

A small business owner wants to integrate Shopify into their existing website to replace PayPal buttons and dropdown menus. They need to handle hundreds of products across multiple categories, each with variants (like color) and customizable add-ons.

Key Challenges:

  • Managing large product catalog with category-based dropdown selections
  • Supporting product variants and additional customizable parts/add-ons
  • Maintaining existing website structure while switching payment systems

Recommended Solutions:

Option 1: Shopify Buy Button Channel

  • Embed products or collections via copy-paste HTML/JavaScript code
  • Generate buttons for individual products or entire collections
  • Includes built-in variant dropdowns and cart functionality
  • Works with any external website platform

Option 2: Storefront API / Buy SDK

  • Provides full custom control for advanced implementations
  • Allows dynamic product fetching and custom dropdown designs
  • Maintains Shopify’s secure checkout process

Add-on Implementation:
Add-ons can be configured as product variants (e.g., “Gasket Add-on” with choices like Rubber, Cork, Silicone) or managed through bundle apps from the Shopify App Store.

The original poster acknowledged the suggestions as helpful starting points.

Summarized with AI on October 24. AI used: claude-sonnet-4-5-20250929.
1

I’m brand new to shopify. I have been running my own small business and created a website that until now uses paypal buttons and drop down menu carts for my products. I’d like to instead start using shopify and simply replace the paypal buttons/dropdowns on my existing website.

I think I understand how to do this with individual buttons for individual products. The problem is that I literally have hundreds of products under dozens of categories, and I want the customer to be able to choose any number of different products in a category from a drop down menu, and choose variants like color etc. Complicating things further is that each “product” also comes with a variety of additional parts that the customer can choose from. For example, one category has 15 different products, and each product can come with 1 “add-on” for the same price but the customer needs to choose the add-on and color.

I have no clue how to go about this so if someone could point me in the right direction I’d appreciate it.

2

Checkout & Add to cart buttons: these will be through a default product template that you customize using the theme customizer. At the center top you will see the template you are working on. Product pages, unless specified otherwise, will use the same template. You edit the template, it will edit all product pages that use that template.

“Add-ons” can be in the form of variant or a bundle app from the Shopify App Store. For example, sizes are variants. Colors are variants. You can also have a customer select an “add-on using the same variant method. “Gasket Add-on” can be a variant and the choices can be “Rubber”, “Cork”, and “Silicone”. Another method is by using a bundle app, where you create a product bundle that comes with a,b, or c.

3

It’s a great Question. And you are in a very common but tricky position.

Shopify has a feature exactly for this: the Buy Button Channel.
This lets you embed Shopify products or collections into any external website (WordPress, custom HTML, Wix, etc.) via copy-paste HTML or JavaScript code.

Two Approaches to Choose From

1. Use Shopify Buy Button for Each Product or Collection

This is the most common way to integrate Shopify into an existing site.

  • In Shopify, you create all your products, variants, and add-ons as you normally would.

  • Then you use Shopify’s Buy Button channel (found in your Shopify admin under “Sales Channels → Buy Button”).

  • You can generate:

    • A button for a single product (with variant dropdowns, quantity selector, and cart popup)

    • Or a button for an entire collection — this shows multiple products in one embedded widget.

You then copy the HTML code Shopify gives you and paste it into your existing page where your PayPal buttons used to be.

2. Use a “Storefront API” or “Shopify Buy SDK” for Full Custom Control

If you want something more customized (e.g. your dropdown menus dynamically show Shopify products, add-ons, or categories), you can use Shopify’s Storefront API or Buy SDK (JavaScript).

This option:

  • Lets you fetch products and variants dynamically.

  • Lets customers choose from dropdowns or selectors you design.

  • Still uses Shopify’s secure checkout.

By following the above one methods then you can have a solution for your concerns.

4

Thanks for the replies. This gives me some places to start.