[Horizon] Show pre-purchase confirmation checkboxes and block the Add to Cart button until all are checked

Add a single "Pre-purchase Checkbox" block to your Horizon product page to show up to three confirmation checkboxes — terms of service, return policy, and so on. While even one checkbox is left unchecked, an overlay blocks the Add to Cart button and accelerated-checkout buttons like Shop Pay together.

How to add it (1): Add the block via the code editor

◆Shopify admin → Online Store → Themes → "…" → Edit code

◆In the blocks folder, create a new file named pre-purchase-checkbox.liquid and paste the purchased code, then save

How to add it (2): Add the block in the theme editor

◆Theme editor → Product page template → "Product information" → "Details" → "Add block" → select "Pre-purchase Checkbox"

Settings

◆Checkbox items 1–3: a checkbox is shown for each item you fill in. Blank items are hidden
◆Message shown when unchecked: the text shown inside the overlay (use <br> for line breaks)

How it works

While any checkbox is left unchecked, an overlay is layered on top of the element that wraps the Add to Cart and accelerated-checkout buttons, blocking clicks. Instead of disabling each button individually, this approach covers the whole button group — including Shopify's native payment buttons like Shop Pay, which can't be disabled directly via JavaScript.

See the Dawn version here → [Dawn] Show a checkbox on the Dawn theme's product page and enable the buy button once all boxes are checked