To add a logo to your website navigate to Appearance → Site Identity and click on Select image in the Logo section.
There’s no such thing as recommended logo sizes, as logos are displayed in their original size and will not be downscaled. Make sure you resize your logos accordingly before uploading them to WordPress in a graphic app (for example Photoshop).
Serving unscaled images in their original sizes will ensure fast loading times of your website.
To make your logos look crisp on Retina devices, there’s integrated support for displaying Retina-ready versions of your logo images. Simply upload a logo with the same file name and
@2x suffix. For example, if your logo file is called
site-logo.png, you need to upload
Retina versions are twice as large as the original ones. For example, if your logo is
100px x 50px, the Retina version must be
200px x 100px.
Image logos are optional. You may use your site title instead of a logo. Simply remove the logo image and it will automatically fallback to your site title.