Custom CSS
Site-wide CSS escape hatch (max 128 KB), sanitized against style/script breakout. Injected on public and admin shells.
Custom CSS
Site-wide CSS when you need tweaks beyond the Design editors.
Where to find it
Admin → Design → Custom CSS (/admin/design/custom-css)
Setting key: design.site.custom_css_v1
Default empty. Max 131072 characters (128 KB). Empty CSS is allowed.
How it works
Paste CSS in the editor. Saved CSS is sanitized against </style / </script breakout - do not inject raw HTML. Prefer stable public hooks (e.g. .xf-public-main, .xf-site-button).
Injected from the root layout (can affect more than marketing pages). Prefer Design editors when they cover the change.
Common problems
Save fails after a huge paste
You exceeded the character limit - trim the CSS.
Overrides break after an upgrade
Re-check selectors after product updates.