Under Settings > Basic, you can choose to Force SSL links so that your knowledge base will load using "https" rather than "http". SSL links ensure that all data passed between the visitor and the site is encrypted.
All KnowledgeOwl subdomains can use SSL links and have the option to Force SSL (http links will redirect to https). However, if you have a private domain, you will need to add your site SSL certification, chain, and key to make SSL links works.
We recommend everyone choose Force SSL links. It will soon be the default for all new knowledge bases, and Google Chrome will be marking all HTTP websites as "insecure" starting in July, 2018.