Shopify AI theme moves storefront code back to HTML
Shopify is previewing an unnamed HTML-heavy base theme meant to replace Horizon, cutting code lines by 93% as Sidekick edits rise.
By Renata Fuchs · Policy Reporter
· 3 min read
Shopify is previewing a Shopify AI theme that rewrites its storefront base around readable HTML and Liquid rather than JSON-heavy configuration. The company says the unnamed theme has 93% fewer lines of code than Horizon, the current base theme many merchants use to customize Shopify storefronts.
The move is aimed at two audiences Shopify now has to serve at once: human developers reading templates and AI agents modifying them. Ben Sehl, Shopify’s product director for storefronts, wrote on X that major AI models already understand HTML because it is “expressive, local, and token-efficient.” Shopify has not given the theme a public name or a general release date, and it is presenting the work in developer forums as the likely successor to Horizon.
What is Shopify's new AI theme?
Shopify’s new theme is a storefront base theme built mostly in HTML, with Shopify’s Liquid templating language inserted where dynamic behavior is needed. Instead of opening a templates folder and finding long JSON files, merchants and developers would see plain-text files that describe page structure more directly.
Horizon gave merchants more visual control through Shopify’s Online Store Editor, including page blocks and detailed customization settings. Sehl said that flexibility came with a cost: templates became serialized JSON outputs rather than files a developer could understand by reading them directly. In his description, JSON was useful for configuration but a poor surface for editing and reasoning about storefront pages.
Why Shopify is changing its theme architecture
Shopify’s AI assistant, Sidekick, is a major reason for the redesign. Sehl said 20% of Shopify merchants have used Sidekick to edit themes this year, producing 25 million edits. Shopify’s conclusion is that AI agents perform better when code is explicit, readable and structured with clear rules, which overlaps with what human developers want from a maintainable theme.
The company is keeping existing Liquid themes as a “forever API,” according to Sehl, which suggests Shopify is trying to avoid forcing an immediate migration for merchants and agencies with current storefronts. The new work sits on top of changes to Liquid itself, including a new syntax and parser designed to support more complex backend instructions while still exposing simpler typed blocks alongside ordinary HTML.
One of the central additions is a composable block tag, which can hold nested parameters for page components. Sehl compared those parameters to React props, though Shopify’s approach does not require a virtual DOM. Shopify is also adding a partial primitive so parts of a page can update without requiring the full page to re-render, and standard actions for site events such as cart updates.
Sehl said the partial primitive alone should allow Shopify to remove thousands of lines of reactivity code from Horizon. The company has also created 20 rules for generated themes, covering contracts, structure, validation, complexity, nesting and file-size limits.
Liquid is gaining more conventional programming features as part of the work, including Boolean expressions, infix operators with precedence, and literal arrays and objects. Shopify also plans to support Tailwind CSS at some later point, though timing was not disclosed.
The broader signal is that AI tooling is pushing a large commerce platform back toward code that humans can inspect. Shopify’s bet is that an agent editing a storefront and a merchant trying to add another button both benefit when page structure is visible in HTML rather than buried in configuration.
This story draws on original reporting from The Register.
