- Short answer
- Shopify theme Custom CSS is limited to 1,500 characters for the whole theme and 500 for a specific section.
- Where each limit applies
- Theme settings > Custom CSS (whole theme); Custom CSS at the bottom of a section's properties panel.
- Not covered
- Checkout: Custom CSS isn't supported on the Checkout page.
- Beyond length
- Some at-rules, the content property and, currently, URLs outside cdn.shopify.com are blocked too.
- Editor changes on a theme update
- Theme Store themes: theme editor customizations are copied over; recheck that your selectors still exist.
- Code edits on a theme update
- Included if they don't conflict; if incompatible, all your code changes are removed in the updated copy.
How many characters does Custom CSS allow?
Shopify's Help Center caps both levels of Custom CSS: CSS rules that affect the entire theme are limited to 1,500 characters, and rules that affect a specific section to 500.
The theme-wide field, under Theme settings > Custom CSS, affects all online store pages except Checkout, where Custom CSS isn't supported. The section field sits at the bottom of the section's properties panel, and its CSS is scoped to that section.
What else does Custom CSS restrict?
Length isn't the only rule:
- The at-rules
@import,@charsetand@namespacecannot be used. - Section-level CSS permits only
@media,@container,@layerand@supports. - The
contentproperty isn't available. - URLs may currently come only from the cdn.shopify.com domain.
Stay in Custom CSS or move to theme code?
For adjustments the theme editor can't make, Shopify points to editing your theme's code — but only if a Shopify app can't make the change either.
Staying in the editor: on themes installed from the Shopify Theme Store, customizations made using the theme editor are copied over to the updated theme, and Shopify's 2023 announcement of Custom CSS said themes would transfer their custom CSS automatically. After an update, check that your selectors still exist in the new version: an update might stop your CSS from working.
Moving to code: code edits are included in the update if they don't conflict with it; if they are incompatible, all your code changes are removed in the updated copy. Shopify lists customizing or troubleshooting themes with significant code changes among tasks it can't help with.
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