SharePoint 365 and Designer

Dear MLEONKC,

Thank you for reaching out to the Microsoft community. We are delighted to offer our assistance.

In the past, SharePoint Designer was commonly used to create customized master pages for SharePoint sites. However, with modern sites, SharePoint Designer is no longer recommended for customizing sites. Microsoft has deprecated SharePoint Designer and is no longer actively developing it. As an alternative, Microsoft recommends using SharePoint Framework (SPFx) for customizations in SharePoint Online.

Thank you for your understanding and cooperation! Have a great day.

Sincerely,

Sean | Microsoft Community Moderator

Dear MLEONKC,

Thanks for your reply!

In SharePoint Online classic experience only, you can still customize master pages, although there are some differences compared to the on-premises versions. You can use Design Manager to create a custom master page. These master pages allowed extensive customization, including custom JavaScript, CSS, and layout adjustments.

Modern site pages are designed to be fast, easy to author, and responsive across devices. Custom master pages are not supported for modern team sites in SharePoint Online. You cannot directly create or customize master pages as you did in the classic experience.

For reference: Overview of Design Manager in SharePoint | Microsoft Learn

Have a great day.

Sincerely,

Sean | Microsoft Community Moderator

Thanks! Question: So before, in 2016 and such, I could go into Designer and make my own masterpage. I could then create a .aspx page that would use that masterpage. In that .aspx page I could code in my own javaScript, JQuery, SharePoint Services or whatever... is that scanario still possible in SharePoint Online?