Minimal and secure way to add custom CSS per-domain
Add custom CSS styles on websites.
The extension does not require permissions to access all data on all websites all the time. Once you start editing CSS on a page, you get a permission prompt specific to that domain. Later, if the CSS for a domain is not used, the permission will be dropped.
There is no UI clutter of any kind. The entire extension consists of a big editable area for CSS code for the current domain.