The URL is also encrypted on a https connection, they can only see you’ve connected to Reddit… not what you’re actually browsing: https://blog.mozilla.org/en/privacy-security/https-protect/

HTTPS also prevents your internet service provider (ISP) from seeing what pages you visit beyond the top level of a website. That means they can see that you regularly visit https://www.reddit.com, for example, but they won’t see that you spend most of your time at https://www.reddit.com/r/CatGifs/.