SharePoint Header Site remove

LidorD You cannot remove SharePoint site header completely, but you can hide it by following below steps:

1. Click on settings (gear icon) > Change the look > Navigation > turn OFF site navigation visibility > Save
2. Click on settings (gear icon) > Change the look > Header > Set Layout to "Minimal" > turn OFF site title visibility > Upload white transparent image as site logo and site thumbnail > Save

This will hide the site header. However, small/minimal white horizontal section at the top will be there which cannot be hidden using SharePoint out of the box options.

Related read:

1. New Navigation features for SharePoint team sites 
2. New Site Header Options in SharePoint Online 

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