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
Spotted a bug or want an improvement? Tell us — our team reviews every comment, and good ideas get built. Comments are public and anonymous.
Found a wrong assignment, a missing port, or an edge case?
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