Applying css stylesheet to a specific site/page in Sharepoint Online

Question

I have made a custom search portal for a sharepoint library. As instructed in a different topic here I have selected the stylesheet in the Settings of this site. But it seems this also applies to all top-level sites and document-library views. How do I apply a stylesheet to a single site?

Answer 1

Put a Content Editor WebPart on te page with a LINK to a CSS file.

If it's not a WebPart page you have to go the more technical route:

Use JavaScript, which adds a LINK element to document.head in the MasterPage itself; but you need to check the URL for execution on the correct page

More technical is a Web Scoped UserCustomAction, a JavaScript file which only executes on the Web (and not its SubWebs)
Easy to attach using the SPEditor Chrome Extension:

• https://chrome.google.com/webstore/detail/sp-editor/ecblfcmjnbbgaojblcpmjoamegpbodhd?hl=en