In SharePoint, you can customize the look and feel of your site, but there are limitations to how much you can hide or remove the header part, depending on the version of SharePoint you are using and the specific settings and permissions of your site.
SharePoint Online (Modern Experience): In SharePoint Online, the modern experience is the default, and it provides limited customization options. You can customize the header using the built-in theme and header settings, such as changing the site logo, site name, and navigation. To hide or remove the header completely in modern SharePoint, you may need to use custom scripting and CSS, but this may not be supported or recommended.
SharePoint Online (Classic Experience): In SharePoint Online's classic experience, you have more customization options. You can create custom master pages and use SharePoint Designer to hide or modify the header. However, Microsoft has been moving away from the classic experience, and it's not recommended for long-term solutions.
SharePoint Server (On-Premises): If you are using an on-premises version of SharePoint, you have more control over customization, and it's possible to remove or hide the header by modifying master pages and CSS. However, it's essential to consider the impact on your SharePoint site's functionality and future updates.