These are some frequently asked questions with links to their answer pages.

About Nmap

• How should Nmap be capitalized?
• What is Nmap's license?
• How can I get started contributing code to Nmap?

Port Scans

• What does "tcpwrapped" mean?
• Why does Nmap show some of my ports as "filtered"?
• How can I evade IDS/IPS/firewalls?
• I know this port is open, so why doesn't Nmap show it as open?
• Why is my scan taking forever?

Service Version Detection

• Why do some services have a question mark (?) after them?

OS Detection

• Nmap detected the wrong OS for my host.
• What does "conditions not ideal" mean?

NSE

• This NSE script I downloaded won't work.

Output

• Why is X missing from the Grepable output?

Options and Arguments

• What happened to --interactive?

Bugs

• How do I file a bug report?