UDP Port Scanner
Run an Nmap UDP scan from our servers against an address you own, on the most common UDP services or on a custom list of ports.
- Runs on our servers
- Free to use
About this tool
UDP services are easy to forget because they do not show up in most web-focused checks, yet an open DNS resolver, NTP server or SNMP agent can be abused for amplification attacks or leak information. The UDP Port Scanner runs Nmap in UDP mode from our servers against an address you control and reports each port as open, closed or open|filtered.
Because UDP has no connection handshake, scans are slower and verdicts less definitive than for TCP; the notes under the result explain how to read them. The TCP Port Scanner complements this tool for a complete exposure review.
How to use it — quick steps
- 01
Enter the ip address
Type or paste the ip address in the field above. The lookup runs from our servers, not from your device.
- 02
Adjust the options
Pick the settings that fit your case; the defaults work for most people. They apply on the next run.
- 03
Press "Scan UDP ports"
Press "Scan UDP ports" or Ctrl + Enter. The result appears below in a few seconds. Results can be copied.
Key features of this tool
External lookups
The lookup runs from our infrastructure, so you see what the public internet sees without exposing your own IP address or network.
Fast and cached
Results come back in seconds; identical lookups are cached for a few minutes to keep the service fast and responsive for everyone.
Easy to reuse
Every result block can be copied with one click or downloaded as a text file, and tables can also be saved as CSV for your reports.
Frequently asked questions
Why does UDP show "open|filtered" so often?
UDP has no handshake. If a port does not answer a probe, Nmap cannot tell whether a service silently ignored it or a firewall dropped it, so it reports both possibilities.
How does Nmap know a UDP port is closed?
A closed UDP port makes the host send back an ICMP "port unreachable" message. Hosts that rate-limit ICMP make UDP scans slow, especially when scanning multiple ports across large networks.
Which UDP services matter most?
DNS (53), NTP (123) and SNMP (161) are frequently abused for amplification attacks when left open; SSDP (1900) and memcached (11211) are other classics worth checking.