Masscan
Masscan is an asynchronous TCP port scanner built for speed, able to cover very large address ranges far faster than traditional scanners.
Legal & ethical use. Use this tool only on systems, networks and data that you own or have explicit written permission to test. Unauthorised access or scanning can break computer-misuse laws (for example Pakistan's Prevention of Electronic Crimes Act, 2016, and equivalents elsewhere). Practise in your own lab or in authorised environments such as CTFs.
What it is used for
- Survey open ports across a large address space you are responsible for
- Quickly find which hosts expose a single port (for example 443)
- Feed results into a slower, more detailed scanner
Key features
- Very high packet rates with its own TCP/IP stack
- Nmap-like command-line options
- Selectable output formats
- Rate limiting (--rate)
Installation
Build from source following the repository README (needs a C compiler and libpcap headers) or use your distribution package where available.
Beginner usage guide
Because it can saturate links, always set an explicit --rate and test on a small range first. Use it to find candidate hosts and ports, then verify interesting results with Nmap.
Example commands
Run these only against your own lab or authorised targets. Placeholder addresses such as 192.0.2.x are documentation ranges.
Scan a lab range for port 80 at a low rate
masscan 192.168.56.0/24 -p80 --rate 100Looks for open port 80 across the lab subnet while sending at most 100 packets per second.
References
Source verification
Last reviewed: 2026-10-27
Links checked over HTTP: 2026-10-27 07:51 UTC — official: 200, docs: 200, repo: 200
Command flags checked against the real binary masscan (Masscan version 1.3.2 ( https://github.com/robertdavidgraham...) on 2026-10-27.