What to check before you publish a theme update

An updated theme can pass every automatic check and still lose your best-selling page's size chart. This is what we look at before publishing, on our own client stores and in Molt. You can use the same list with Shopify's own update.

Look for what the release took away

New features announce themselves in the release notes. Removals are easier to miss. When we upgraded a customized Dawn from 15.4.0 to 16.1.1, the new defaults removed 16 parts of the store that nobody had edited. They included footer columns, the cart's featured collection and four product page rows.

Go through your home, product and cart pages section by section. Compare with your live theme in a second window. Anything you want back can usually go back in the theme editor, if the new release still includes that section.

Check the pages your customers use most

Open these on the draft:

• Your home page
• Your best-selling product, on a phone
• A collection, with its filters
• Search results
• The cart, with something in it
• Any page with a custom template

Then do what a customer does. Choose a variant, add to the cart, change the quantity and start checkout. A screenshot shows the page, and only a click shows whether the cart drawer opens.

Test your custom code one piece at a time

List your customizations and check each one where it appears. If you have a size guide, open it. If you have a free shipping bar, add enough to the cart to reach the threshold.

Shopify's update page gives one tip that catches a lot: check that your custom CSS selectors still exist. A release that renames a class leaves your rule in the stylesheet, and it quietly stops applying.

Check your customer accounts

Dawn removed its classic customer account pages in 16.0.0. New customer accounts carry on as they were, because Shopify hosts those pages. On classic accounts, your login and order pages depend on those templates. Find out which you use under Settings, Customer accounts before you publish.

Check apps that add code

Apps can write into theme files. If one added a snippet to a section the release rewrote, its widget can disappear. Open the pages where your apps appear, especially reviews and subscriptions.

Know your way back

Before you publish, know how to undo it. Your previous theme stays in your themes list, and publishing it again takes seconds. Keep a separate copy of the code too. Then publish at a quiet time, and look at the live store right after.

Molt runs the page comparison and lists removals and customizations for you. You still do the part where you act like a customer.