If you want a clickable website link within a post or on a profile on Mastodon, remember to include https:// at the beginning when you’re writing it. This tells the server that you want the link to be clickable.
Some other social networks automatically change anything with a dot in the middle into a clickable link, but this doesn’t happen on the Fediverse because some people want to include dots without making clickable links.
Can I make other types of links clickable on Mastodon?
Yes! As well as website links, you can also use many other kinds of links. All of these will work as clickable links on Mastodon: https://, http://, gemini://, dat://, dweb://, gopher://, ipfs:// and ssb://
Note that the Gemini link type is nothing to do with AI or Google. The Gemini protocol is from 2019 and is intended as a lightweight simpler alternative to the web ⧉.