Free IP Scanner — Scan Any IP for Open Ports & Vulnerabilities
Scan any IP address for open ports, running services, and vulnerabilities — completely free. Zondex lets you look up any IP instantly without running your own scanner.
What Is IP Scanning?
IP scanning (also called port scanning) is the process of probing an IP address to discover which network ports are open and what services are running on them. Every internet-connected device has 65,535 TCP and 65,535 UDP ports. An IP scanner sends packets to these ports and analyzes the responses to determine which services are listening.
IP scanning is a fundamental technique in cybersecurity. Network administrators use it to audit their own infrastructure, penetration testers use it during the reconnaissance phase, and security researchers use it to study the internet at scale.
While tools like Nmap let you actively scan individual targets (requiring authorization), passive IP scanners like Zondex let you look up pre-scanned data on any IP without sending a single packet to the target.
How Port Scanning Works
TCP Connect Scan
Completes the full TCP three-way handshake (SYN → SYN-ACK → ACK). Most reliable but easily logged — Nmap's -sT flag.
SYN Scan (Half-Open)
Sends SYN and waits for SYN-ACK without completing the handshake. Faster and stealthier — used by ZMap, Masscan, and Zondex.
Banner Grabbing
After identifying open ports, the scanner connects and captures the service banner — software, version, and configuration.
How to Use Zondex as a Free IP Scanner
Zondex maintains a continuously updated database of scanned IP addresses. Instead of running your own scan, you can instantly look up any IP address to see its open ports, services, and vulnerabilities.
Active Scanning (Nmap, Masscan)
- ⚠ Sends packets directly to the target
- ⚠ Requires authorization from network owner
- ⚠ Can trigger IDS/IPS alerts
- ✓ Most up-to-date results
- ✓ Customizable scan depth
Passive Lookup (Zondex)
- ✓ No packets sent to target
- ✓ No authorization needed
- ✓ Completely undetectable
- ✓ Instant results (sub-second)
- ✓ Historical data available
Frequently Asked Questions
What is an IP scanner?
Is IP scanning legal?
What is the best free IP scanner?
What is the difference between active and passive IP scanning?
How do I scan my own IP for open ports?
Scan Any IP Address — Free
Look up open ports, services, and vulnerabilities on any IP. No installation required.