Thumbnails

Thumbnail size

All thumbnails in WordPress has default size 150x150px. This sometimes causes that images are blurred. To fix that you should do 2 simple steps.

Set thumbnail size to larger

In WordPress admin go to Settings > Media and set Thumbnail size at least to 300x300px and Medium size to 600x600px.

Regenerate thumbnails

At first install Regenerate Thumbnails plugin from wordpress.org. After successful installation and activation regenerate thumbnails.