Free Online Port Scanner

Powered by Nmap — the industry-standard network scanner. Discover open ports, running services, and their versions.

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Quick answer

A port scanner is a tool that checks which network ports on a server are open and what services are running behind them. Secably's port scanner is powered by Nmap, detects service names and versions, is free, and requires no signup.

  • Powered by Nmap, the industry-standard scanner
  • Detects open ports plus service and version
  • Top 100 ports free, all 65,535 on Pro
  • No signup, results in seconds

What is a port scanner?

Every server communicates through numbered ports — port 443 for HTTPS, 22 for SSH, 3306 for MySQL, and so on. A port scanner checks which of these ports are open and reachable, and identifies the service — often the exact version — listening on each one.

An open port is a door. Some are meant to be open, like your website on port 443. Others — a database on 3306, an admin panel, a forgotten dev service — should never face the public internet. A port scan tells you which doors are open before an attacker checks for you.

Why open ports matter for security

Every exposed service is a potential entry point. An outdated service on an open port, a database with no firewall, or remote access (RDP/SSH) reachable from anywhere is exactly what attackers scan the internet for.

The stakes are rising: exploited vulnerabilities are now the starting point for 20% of breaches, a 34% jump in a single year (Verizon DBIR, 2025) — and every one of those vulnerabilities is only reachable through an open port. Knowing exactly what you expose is the first line of defense.

How a port scan works

Secably runs Nmap — the industry-standard network scanner — against your target, then reports each port's state and the service behind it.

— Probe

TCP connection probing

Nmap attempts a connection to each port and records whether it is open, closed, or filtered by a firewall.

— Fingerprint

Service & version detection

For each open port, Nmap fingerprints the service and its version — for example OpenSSH 8.9 or nginx 1.24 — so you know what's actually running.

— Coverage

Port selection

The free scan covers the top 100 most-targeted ports. Pro scans all 65,535, so nothing hides on a high, unusual port number.

Port states, explained: open means a service is actively listening; closed means the port is reachable but nothing is listening; filtered means a firewall is dropping the probe, so the state can't be confirmed.

How to scan ports in 3 steps

1

Enter a domain or IP

Type a hostname like example.com or an IP address. Secably resolves and scans it.

2

Choose a port range

Scan the top 100 ports for a fast overview, ports 1–1000 for common services, or all 65,535 on Pro.

3

Read the results

Every open port is listed with its service and version. Save or export the full report with a free account.

Who uses a port scanner

dev
Confirm only what you meant to expose
Developers: after a deploy, verify that only your intended ports (like 80 and 443) are reachable — not a debug server or database you forgot to firewall.
ops
Audit servers from the outside
Sysadmins & ops: catch accidentally-exposed databases, admin panels, and remote-access ports (RDP/SSH) before they're found for you.
sec
Map exposed services during recon
Security & pentesters: enumerate open ports and running versions in one pass, and prioritize the risky services for deeper testing.

Frequently Asked Questions

What is a port scanner? +
A port scanner probes a server to find which network ports are open and what services are running on them. It's the first step in understanding a server's attack surface.
Is this tool powered by Nmap? +
Yes. Secably uses Nmap with service version detection to identify running services. The free tier scans the top 100 most common ports; Pro scans all 65,535.
What is an open port? +
An open port is one where a service is actively listening and accepting connections. Open ports are how servers offer services like websites, email, and databases — and each one is a potential entry point.
What's the difference between open, closed, and filtered? +
Open means a service is listening. Closed means the port is reachable but nothing is listening. Filtered means a firewall is dropping the probe, so the port's true state can't be determined.
Which ports are the most important to check? +
Commonly exposed and high-risk ports include 22 (SSH), 23 (Telnet), 3389 (RDP), 3306 (MySQL), 5432 (PostgreSQL), 6379 (Redis), and 27017 (MongoDB). Databases and remote-access ports should rarely be open to the public internet.
Does it scan TCP or UDP ports? +
This tool scans TCP ports, which host the majority of exposed services. UDP scanning is available in deeper scans for services like DNS, SNMP, and VPNs.
Is it legal to scan ports? +
Only scan infrastructure you own or have explicit authorization to test. Unauthorized port scanning may violate laws in your jurisdiction. Secably is intended for assessing your own assets.
What's the difference between free and Pro? +
Free scans the top 100 ports with 3 scans per day. Pro unlocks all 65,535 ports, unlimited scans, API access, export, and scheduled monitoring with alerts.

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