Quick Reference
Parameter | What it does | Example |
| Pre-selects a pack size |
|
| Adds an item by Variant ID |
|
| Adds an item by product handle |
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How do I pre-add a product?
Add ?add_variant=VARIANT_ID to your product URL:
https://yourstore.com/products/build-your-box?add_variant=48372615930123
Where do I find the Variant ID?
Go to Shopify Admin → Products
Click on the product, then the specific variant
The number after
/variants/in the URL is your Variant ID
Example URL: https://admin.shopify.com/store/mystore/products/123/variants/48372615930123 → Variant ID: 48372615930123
How do I pre-add multiple products?
Add multiple add_variant parameters separated by &:
https://yourstore.com/products/build-your-box?add_variant=12345&add_variant=67890&add_variant=11111
Can I use product names instead of variant IDs?
Yes — use add_product=PRODUCT_HANDLE to add the first available variant. The handle is the URL-friendly name (e.g., yourstore.com/products/truffle-pizza → handle is truffle-pizza):
https://yourstore.com/products/build-your-box?add_product=truffle-pizza
How do I pre-select a pack size?
Add ?pack_size=NUMBER (must match an available pack size):
https://yourstore.com/products/build-your-box?pack_size=6
Can I combine parameters?
Yes — combine with &:
https://yourstore.com/products/build-your-box?pack_size=6&add_variant=12345&add_variant=67890
This opens the 6-pack with 2 items already added.
What happens when a customer clicks the link?
Page loads with Pack Builder
Pack size is set (if specified)
Items are added to the pack
URL is cleaned up (parameters removed to prevent duplicates on refresh)
Customer continues building normally
Edge Cases
Invalid variant/product — Silently skipped; valid items still added
More items than pack size — Only items up to the pack limit are added; extras ignored
Returning customer with saved pack — URL parameters take priority over saved data
Examples
Facebook Ad for a specific flavor:
https://yourstore.com/products/build-your-box?add_variant=48372615930123
Email with 6-pack pre-selected:
https://yourstore.com/products/build-your-box?pack_size=6
Landing page with size + items pre-filled:
https://yourstore.com/products/build-your-box?pack_size=6&add_product=truffle-pizza&add_product=margherita
Troubleshooting
Pack size not changing — Number must match an available size exactly; use
pack_sizewith underscoreProduct not being added — Verify variant ID in Shopify Admin; for
add_product, handle must match exactly (lowercase, hyphens)Parameters not working — Use
?before first parameter,&between parameters; check for typos