Theme app blocks: why apps don’t edit your theme any more

If you have run a Shopify store for a while, you will remember the older way and probably not fondly.

How it used to work

An app that wanted to show something on your storefront edited your theme. It injected Liquid into your templates, sometimes a script tag into your layout, occasionally a whole snippet file.

Three consequences followed, all bad. Uninstalling frequently left the code behind, so themes accumulated fragments of apps nobody remembered installing. Changing theme meant re-doing every app’s installation. And two apps editing the same template could break each other in ways that were genuinely hard to diagnose.

What a theme app block is

A block an app provides that you add through the theme editor, exactly like a section your theme came with. You add it by dragging it where you want it. You remove it by deleting it.

The important part is that your theme’s files are never modified. The block is the app’s, the theme is yours, and the theme editor is where the two meet.

Why it matters to a merchant

• Removal is clean. Delete the block, and the theme is exactly as it was. Uninstall the app entirely and nothing is left behind.
• Placement is visual. You put the widget where you can see it should go, rather than describing a position to someone in a support ticket.
• No developer. Nothing to paste, nothing to back up first.
• Themes can be changed. The blocks are configured per theme, and a theme you have not set up simply does not show them — which is a much better failure than a broken layout.

The app embed

One piece of vocabulary worth learning, because it trips up almost every first setup. Alongside blocks, an app can have an app embed — a store-wide toggle that lets the app run on your storefront at all.

It lives in the theme editor rather than in the app, which is why it does not feel like part of setting the app up. Until it is on, nothing renders no matter how much you have configured. If something appears to be doing nothing, this is the first thing to check.

The requirement

Theme app blocks need an Online Store 2.0 theme. Dawn, Horizon and every theme published in recent years qualify. If your theme predates that, this is a good reason to update it — not only for apps, but because almost everything modern on the platform assumes it.