Why is the wrong product variant being added to my online store's cart?

Shopify Discussion

Topic summary

Issue: Multiple store owners report incorrect product variants being added to their carts. When customers select specific variants (e.g., queen/medium or king/firm), either the first variant (standard/soft or size small) appears in the cart instead, or previously selected variants duplicate.

Root Cause Identified: A script on the product page fails to load properly, preventing variant selection from updating correctly. The variant ID in the URL (?variant=xxx) doesn’t change when customers select different options, indicating the selection isn’t registering.

Current Status: The issue affects at least two stores using different themes (Symmetry and another). One user requested help fixing the problematic script, but no solution has been provided yet. The discussion remains open with users seeking a resolution.

Summarized with AI on November 2. AI used: claude-sonnet-4-5-20250929.
1

We’re experiencing some incorrect variants being added to cart. I’ve read through all of the discussions here and haven’t found a solution that works for our store/theme. We’re using Symmetry and have noticed the error on our pillows. Example: https://ameridown.com/products/premier-down-feather-blend-pillow?variant=31170924019778

Sometimes the variant showing up in the cart will be the first variant: standard/soft. Other times the variant in the cart will be the same as the variant you just added. For instance, if I add a queen/medium and then add a king/firm, I end up with 2x queen/medium in my cart.

Any ideas?

2

Hi @ameridown ,

I looked at your site and found the issue might be that the script won’t load successfully on the product page.

When that happens, selecting the options (size or support) won’t actually update the variants that is added to the cart. You could replicate it by noticing the ?variant=xxx in your URL. the variant ID suppose to be changed when you change options.

3

Hi @JonathanX

Thanks for pointing that out. I see that the variant ID is not updating in the URL. Can you help me fix the script that’s causing the issue?

4

I am having the same issue. No matter what variant I choose, the only variant that shows up in the cart is the first option size small. Did you have a fix for this? You can test it out here https://www.bootywrap.com/products/black-bootywrap. If you add medium or large to the cart it always says small.