Minify your CSS by removing all the unnecessary characters.
Minify your JS by removing all the unnecessary characters.
Validate JSON content and make it looks good.
Get details of any file type, such as the mime type or last edit date.
Get approximate IP details.
Check whether or not a website is using the new HTTP/2 protocol or not.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Make sure your passwords are good enough.