What kind of users do you want to recruit for usability testing?

Employees only. They understand your content so you won’t have to waste time explaining the content during the usability test.
Customers only. If you know what they like, you can make the best experience for everyone.
Non-customers that have visited your website before. This user segment is the most important since they are near the end of their buyer’s journey.
Both customers and noncustomers. A mix of the two emulates your current website traffic to make a good usability test.