There is no Purity app for Shopify. Add Purity's add-to-cart buttons to your Shopify theme: buyers pick products on your Shopify pages and pay on your Purity checkout, so the order, payment code and stock all live in Purity. Shopify's own checkout is not used for these products.
Open Website, choose Shopify under "Where do you sell today?", then follow these steps:
- Create a site key. It lets your site show live prices and stock. Use "Create a site key" or "Create a secret key" on the Website page.
- Copy this code. The Website page has this ready to copy.
- In Shopify: Online Store > Themes. On your live theme choose the three dots (...) > Edit code. Open layout > theme.liquid, paste the code just above the closing </body> line, and choose Save.
- Put this on any button or link that should add a product to the cart. Change YOUR-SKU to the product's SKU in Purity. The Website page has this ready to copy.
- Publish your site, then paste your site address below and choose "Check my site". Purity looks for the code on your page.
Connected looks like: Purity finds the code on your page and shows when your site last loaded your products.
Stock: the buttons read Purity's live stock every time a page loads, and orders are placed on your Purity checkout, so a sale takes stock off in Purity at once and sold-out products update on their own (Sold out, Pre-order or hidden, as you choose under "Stock on your website"). Purity does not change the stock count in Shopify's own inventory: there is no Purity app for Shopify, so if you also sell a product through Shopify's checkout, Shopify will not know about Purity sales.
Read Shopify's rules on what can be sold before building on it. Many research compound stores have had Shopify stores closed. Their rules: https://help.shopify.com/en/manual/payments/shopify-payments/eligibility