DNS across resolvers
Ask four public resolvers the same question and see whether they agree. Useful for checking propagation after a record change.
Redirect chain
Follow a URL one hop at a time and see every status code, Location header and cache header on the way.
TLS versions and ciphers
Lists the TLS versions a server enables and every cipher suite it accepts, in the order it prefers them.
Takes 5–20 seconds. Sites served through Cloudflare can't be scanned yet.