Free Port Number Lookup – Search TCP/UDP Ports by Number or Name

Understanding TCP/UDP Port Numbers and Their Role in Networking

A port number lookup tool lets you search for a specific TCP or UDP port number and instantly see which service or protocol conventionally uses it, along with a brief security assessment. Every network connection on the internet is identified not just by an IP address but by a 16-bit port number (0–65535) that directs traffic to the correct application on the receiving host. IANA (the Internet Assigned Numbers Authority) maintains the official Service Name and Transport Protocol Port Number Registry, dividing the range into well-known ports (0–1023, assigned to core protocols like HTTP/80, HTTPS/443, SSH/22), registered ports (1024–49151, used by application vendors), and dynamic/ephemeral ports (49152–65535, assigned temporarily by the OS for outgoing connections). This tool covers the roughly 100 ports that people actually look up in practice. When a browser connects to https://example.com, it opens a TCP socket to the server's IP on port 443; the server listens on that port because the TLS/HTTPS convention established by RFC 2818 designates it. Similarly, SSH listens on port 22 (RFC 4253), SMTP on 25 (RFC 5321), DNS on 53 (RFC 1035, both TCP and UDP), and MySQL on 3306 by convention. The tool's curated list includes protocol name, a plain-language description of what the port does, whether it uses TCP, UDP, or both, a category tag (web, mail, database, remote-access, file-transfer, gaming, network, other), and an optional security note warning when the protocol is unencrypted or otherwise risky to expose to the public internet. Searching for port 3306, for example, returns MySQL with a note that it transmits credentials in plaintext unless TLS is configured, and that exposing it directly to the internet is a common attack vector for brute-force and SQL-injection campaigns. Port 6379 shows Redis with a warning that it ships with no authentication by default and should never be bound to a public interface. Port 25 (SMTP) notes that residential ISPs routinely block outbound port 25 to prevent spam relays, and that submission on port 587 with STARTTLS is the modern alternative for sending mail from a client. These context notes turn a dry lookup into actionable guidance. System administrators use this when writing firewall rules: before opening a port on a production server, they confirm which service expects it and whether an encrypted alternative exists. Developers debugging a connection timeout search by service name ("PostgreSQL") to confirm the default port (5432) matches their configuration. Penetration testers identify services running on non-standard ports by cross-referencing scan results with the well-known list to spot anomalies. Students studying for the CompTIA Network+ or CCNA memorise the classic ports and use this as a quick-check reference during practice labs. This reference is curated, not exhaustive: it covers approximately 100 of the most commonly queried ports rather than IANA's full 8,000-plus registered entries, because the vast majority of those are obscure legacy protocols nobody will ever search for. If a port is not in the list, the tool says so clearly rather than guessing. A common misunderstanding is treating a port number as inherently secure or insecure; the number itself is just a routing label, and safety depends entirely on the protocol running on it and whether that protocol is encrypted. Port 22 is safe because SSH encrypts everything, while port 23 is dangerous because Telnet sends passwords in the clear over the identical transport. That is why the security notes describe the protocol's behaviour rather than the number. Every lookup is a simple client-side filter on a static in-memory table — no network request is made, no external API is called, and no query data leaves your browser, so the reference works identically whether you are online or offline.

Port Number Lookup Formula & Method

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