Check any domain or IP for open ports and exposed services. Scans 20 high-risk ports including SSH, RDP, SMB, databases, and mail servers.
Frequently asked questions
What ports does this scanner check?
The free scanner checks 20 high-risk ports commonly targeted by attackers: FTP (21), SSH (22), Telnet (23), SMTP (25), DNS (53), HTTP (80), POP3 (110), IMAP (143), HTTPS (443), SMB (445), MSSQL (1433), Oracle (1521), MySQL (3306), RDP (3389), PostgreSQL (5432), VNC (5900), Redis (6379), HTTP-Alt (8080), HTTPS-Alt (8443), and MongoDB (27017).
Why is an open port dangerous?
Open ports expose services to the internet. If a service has known vulnerabilities, weak authentication, or misconfiguration, attackers can exploit it to gain unauthorized access. Database ports (MySQL, PostgreSQL, MongoDB, Redis) and remote access ports (RDP, VNC, Telnet) are especially dangerous when exposed without proper access controls like VPN or IP whitelisting.
Does this work through Cloudflare or other CDNs?
Yes. The scanner detects CDN proxying and adjusts results accordingly. Web ports (80, 443) behind a CDN reflect the CDN edge, not your origin server. Dangerous service ports (databases, RDP, SMB, VNC) probe through to the origin directly, so those results remain accurate even behind Cloudflare.
How is this different from nmap?
This scanner runs entirely from Cloudflare's edge network using TCP connect probes — no software to install, works from any browser. It focuses on the 20 most commonly exploited ports for quick exposure assessment. For comprehensive scans of all 65,535 ports, service banner grabbing, and OS fingerprinting, use nmap locally or upgrade to Port Scanner Pro.
Need a full port sweep? Upgrade to Port Scanner Pro.
Scan all 65,535 ports, detect service versions via banner grabbing, and get continuous monitoring that alerts you the moment a new port opens.
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