Port Number Lookup & Range Classifier
Type a TCP/UDP port number or a service name to get its assigned service, transport protocol, IANA range (well-known, registered, or dynamic), the governing RFC, and a security note where the classic protocol is insecure. The range classifier bands any number from 0 to 65535. Runs in your browser, nothing is uploaded.
How it works
This is a reference tool, so the “calculation” is classification and matching rather than arithmetic. Every curated entry is transcribed from the IANA Service Name and Transport Protocol Port Number Registry , the single authority for which service owns which port, and the range bands come straight from RFC 6335 §6.
A port is a 16-bit unsigned integer, so the valid space is 0 to 2¹⁶ − 1 = 65535. RFC 6335 splits that space into three contiguous bands:
- 0 – 1023, System / Well-Known (IANA-assigned; needs root to bind on Unix)
- 1024 – 49151, User / Registered (IANA-assigned on request)
- 49152 – 65535, Dynamic / Private / Ephemeral (never IANA-assigned)
When you type a whole number, the tool classifies it by walking that table and rejects anything that isn't an integer in 0–65535 (a decimal, a negative, or a value above 65535, the classic off-by-one traps are the 1023/1024 and 49151/49152 boundaries, which are handled with inclusive bounds). To keep the classifier honest, a second, independent function re-derives the band using plain threshold comparisons; the calculator shows “both classifiers agree” only when the two methods return the same result, the same cross-check idea used on our tax calculator.
When you type text instead, the tool does a case-insensitive substring match against each entry's service name, human name, and a list of keyword aliases (so “mail” surfaces SMTP, IMAP, and POP3). Protocol and range filters then narrow the list. Entries whose classic protocol transmits credentials or data in cleartext, Telnet, FTP, HTTP, POP3, IMAP, SNMP v1/v2c and others, carry a security flag and point to the encrypted equivalent, each justified by its RFC. All of this happens client-side; the page never contacts a server, so it can't and doesn't scan your network.
Worked examples
Frequently asked questions
Sources & references
- IANA: Service Name and Transport Protocol Port Number Registry
- RFC 6335: IANA Procedures for Port Number Ranges (§6 defines the three bands)
- RFC 6056: Recommendations for Transport-Protocol Port Randomization (ephemeral ports)
The curated port list and range bands were last cross-checked against the IANA registry and RFC 6335 on 2026-07-04. Per-service RFCs (SSH 4253, SMTP 5321, DNS 1035, and others) are linked on each result card. The list covers the highest-search-volume ports; use the IANA registry for the full long tail.
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Comments & feedback
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Found a wrong assignment, a missing port, or an edge case?
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