Company Logo is very important in any organization and SharePoint 2016 or 2013 provides easiest way to use your company logo as well as to change logo. By default the logo appears in the top left corner which looks like below:
The default site logo appears in below size:
Width: 180 pixels
Height: 65 pixels
To change a logo, open SharePoint 2016 site and then click on the gear icon and then click on Site Settings.
Then click on "Title, description, and logo" which is under Look and Feel section.
This is the place where you can change your site Title, Description as well as Logo. Then to insert a Logo you can insert from your computer as well as you can insert it from SharePoint.
When you select Insert from Computer, it will ask you to browse the Logo image file. By default it will upload to SiteAssets document library. Apart from that you can also choose From SharePoint and upload to any document library. It looks like below:
Apart from that if you have multiple site collections and you want to use the same logo then you can upload the logo into 15 hive folder and can give the logo url like below:
Change Logo using PowerShell:
Apart from browser you can also change logo by using PowerShell. Follow below article for the same.
If you have multiple sites and you want to change logo in all sites and sub sites you can follow below article for the same.
Hope this will be helpful.