Will Custom-CSS be lost after a theme update?

Store Design
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Topic summary

A user working with the Horizon theme wants to know whether custom CSS added through the Theme Editor’s “Custom CSS” field will persist after theme updates, or if they should embed styles directly in the code instead.

Answer provided:

  • Custom CSS added via theme settings (“Custom CSS” fields and “Custom Liquid” sections/blocks) will persist through updates
  • This is the recommended approach for non-developers
  • Direct code edits will be lost when the theme updates

Exception noted: Developers using GitHub integration or deployment automations may handle customizations differently.

Summarized with AI on October 23. AI used: claude-sonnet-4-5-20250929.
1

I use a lot of custom CSS in the Horizon theme, which I add via the Theme Editor under “Custom CSS.”

I’d like to know if these styles will be lost when the theme is updated, or should I embed them directly in the code instead? What could you recommend?

2

Nope, this is the recommended[1] way to modify your theme – by using “Custom CSS” settings and “Custom Liquid” sections/blocks.

Since these are theme settings they will persist during theme updates.
But the theme code edits will be stripped during update.

  1. Unless you are a dev/ have Github integration or deployment automations ↩︎

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