Creator Tyler Deitz says:

StreetPass is a browser extension that helps you find your people on Mastodon. It piggybacks off the way Mastodon handles decentralized identity verification and turns it into a simple discovery tool that recommends users based on the websites you visit! Available for Chrome and Firefox (soon Safari).

Discovery is one of the more challenging facets of federated social networking. It gets even more challenging now that Twitter’s API is getting paywall’d, so most of the free tools to port your Twitter social graph over to Mastodon will quit working. I expect more tools like StreetPass to pop up in the coming days as the Fediverse seems to be capturing that hacker spirit Twitter once embraced.