If you can't find or add the SmartSize app block in your theme editor, here are the most common reasons — and how to fix each one.
1. Your theme doesn't support app blocks
SmartSize uses Shopify app blocks, which only work with Online Store 2.0 themes.
Older themes (sometimes called "vintage" or "1.0" themes) don't support app blocks at all. If your theme was built before 2021 or hasn't been updated, this is likely the issue.
How to check:
Go to Online Store → Themes in your Shopify admin
Click Customize on your active theme
Navigate to any product page template
In the left sidebar, look for an Add block (+) option with an Apps section
If you don't see an Apps section when adding a block, your theme doesn't support app blocks.
How to fix it:
Upgrade your theme to a 2.0-compatible version. All free Shopify themes (Dawn, Refresh, Craft, etc.) support app blocks.
If you use a paid or custom theme, check with the theme developer whether a 2.0 update is available.
2. You're on the wrong template
The standard SmartSize app block (Button for size quiz) can only be added to product page templates.
How to fix it:
In the theme editor, open the template dropdown at the top
Select Products → Default product (or whichever product template you use for your products!)
Now try adding the block — you should see Apps → Button for size quiz
Tip: If you want to place a quiz button on a non-product page (like a collection or landing page), use the Button for static size quiz (advanced) block instead. It works on any page but requires you to enter a specific Quiz ID.
4. The block may appear somewhere else below the product section or not appear at all.
Some themes use custom or nested sections for product pages. The app block might only be available outside a specific section — not inside the product section.
If this is the case, you might need some a modification to your theme's code. See example below.
Still not working?
If none of the above solves it, just reply to us through the chat widget or shoot an email to: [email protected] — we'll help you get set up.