Searchable TCP / UDP port reference
A firewall rule mentions some port I half-remember. I tab out to Wikipedia. Again. Got sick of it, so here’s the fix. Type a number, a service name, even a vague keyword like “database,” and the table filters while you type. Narrow it to TCP or UDP. Jump to the well-known range (0 to 1023). Or flag the crusty cleartext stuff you really shouldn’t be leaving open. Every row hands you the protocol, the service, its category, plus a one-line “what even is this.” And it all lives in the page. Nothing you type ever leaves your browser.
| Port▲ | Proto | Service |
|---|
What this common ports list is for
So what is a port, really? It’s a number. It tells the OS which program should catch an incoming packet, nothing fancier than that. Pair it with an IP address and now you’ve got one specific endpoint, which is sort of the whole point of the thing. I look these up constantly. Reading a netstat dump, sanity-checking a firewall rule. Or squinting at a scan report, wondering what on earth is squatting on 9000. So I keep this cheat sheet around: the well-known ports from 0 to 1023, plus the registered ones above that I actually bump into, with search so I never have to scroll.
IANA owns the official registry. It splits the 0-65535 space into three buckets (well-known, registered, dynamic). Out of the box the table sorts low to high by port number. Click any header to re-sort by that column. Start typing to filter live. The category and protocol controls are there for when you only want, say, the database ports and nothing else.
How port numbers and protocols work together
A port number on its own tells you almost nothing until you know the transport sitting under it. TCP and UDP each get their own full set of 65,536 ports, kept completely separate. Which means TCP 53 and UDP 53 are two different doors, even though DNS happens to knock on both. TCP’s the reliable, handshake-heavy one. Most app protocols ride it, HTTP and SSH and SMTP and pretty much anything else you can name. UDP just throws packets and hopes: DNS lookups, DHCP, NTP, VoIP audio, plus the VPN I keep reaching for lately, WireGuard. The Proto column tells you which transport each service speaks. Plenty of them register both anyway.
- Search by number. Something’s listening and you want to know what. Type
8080. - Search by name. Forgot Postgres’ port for the hundredth time? Type
postgres. - Search by keyword to yank up a whole family at once. Try
database,mailorvpn. - Filter by protocol when you only care about TCP. Or only UDP.
- Well-known only drops everything above 1023, for when you just want the classic system ports.
Legacy and insecure ports to watch
A handful of these protocols are old enough that they cheerfully ship your password across the wire in plain text. Anyone sniffing the segment reads it. So I’ve tagged them in the table with a red badge, easy to spot. The ones I’d kill or tunnel before anything else: Telnet (23), FTP (20/21), the Berkeley r-services rexec/rlogin/rsh (512/513/514), TFTP (69), Finger (79), SNMP v1/v2c (161). Encrypted replacements have been around for years (SSH on 22, SFTP or FTPS, SCP, SNMPv3), so the excuses wore thin a long time ago. Mail’s a softer call. POP3 (110) and IMAP (143) are fine wrapped in STARTTLS, technically. I might be in the minority here, but I’d just push everyone to the TLS ports, POP3S (995) and IMAPS (993), and stop thinking about it.
Common ports by category
| Family | Typical ports |
|---|---|
| Web | 80 HTTP, 443 HTTPS, 8080 / 8443 alternates |
25 SMTP, 587 submission, 465 SMTPS, 993 IMAPS, 995 POP3S | |
| Remote access | 22 SSH, 3389 RDP, 5900 VNC, 23 Telnet (legacy) |
| Databases | 3306 MySQL, 5432 PostgreSQL, 1433 MS SQL, 6379 Redis, 27017 MongoDB |
| File transfer | 21 FTP, 22 SFTP, 445 SMB, 2049 NFS, 873 rsync |
| VPN / security | 500/4500 IPsec, 1194 OpenVPN, 51820 WireGuard |
| Infrastructure | 53 DNS, 67/68 DHCP, 123 NTP, 161 SNMP, 389 LDAP |
Privacy and how this tool runs
The whole port list is baked right into the page. The search is plain JavaScript running on your own machine, that’s it. Your keystrokes go nowhere. Nothing gets logged, and there’s no sneaky autocomplete phoning home to some API in the background. Once the page has loaded you can yank the network cable and it keeps working, which is genuinely handy on a locked-down box or an air-gapped lab.
Frequently asked questions
What are well-known ports?
Ports 0 through 1023. It’s the block IANA reserves for the bedrock services, the ones like HTTP (80), HTTPS (443), SSH (22), DNS (53). Here’s the catch on Unix-like systems. A normal user can’t bind a listener down here. You either run as root or hand the process the CAP_NET_BIND_SERVICE capability, no other way around it. That restriction is the exact reason a misbehaving app trying to grab port 80 throws “permission denied” at you instead of just working.
What port does SSH / RDP / MySQL use?
SSH is TCP 22. RDP (Microsoft Remote Desktop) is TCP 3389. MySQL and MariaDB both sit on TCP 3306. Those are the three I get asked about more than anything else, by a mile. Anything else, type its name into the search box up top and you’ll get the port back, the protocol, and a one-liner on what the thing actually does.
What is the difference between a TCP and a UDP port?
They live in completely separate address spaces. That’s the part that trips people up. TCP sets up a connection and guarantees delivery, which is why HTTP and SSH and SMTP all ride on it. UDP skips the ceremony entirely and just flings packets, and that suits DNS, DHCP, NTP, VoIP and WireGuard just fine. The same number on each is a totally different endpoint. So DNS quietly uses both TCP 53 and UDP 53, no conflict at all.
Which ports are dangerous to leave open?
Start with the cleartext dinosaurs: Telnet (23), FTP (20/21), the r-services (512-514), TFTP (69) and SNMP v1/v2c (161). Close them or tunnel them. No exceptions. Then stop pointing your database ports straight at the internet (3306, 5432, 6379, 27017). Redis and Mongo are the worst offenders here, since they ship wide open by default, and people get popped for it constantly. It’s depressing how often. SMB (445) and RDP (3389) belong behind a VPN or an SSH tunnel too.
What is the ephemeral port range?
The top slice, 49152 to 65535. Whenever your machine opens an outbound connection, the OS grabs a free port from here as the source port, uses it for that one conversation, then hands it straight back. Don’t pin a server to a fixed port anywhere in this range. The kernel might already be dishing it out for outbound traffic, and then you’re chasing a flaky “address already in use” that only rears up under load. Painful to debug.
Is this the complete IANA port list?
Nope. And that’s deliberate. The full IANA registry runs to thousands of entries, most of which you’ll go an entire career without ever touching once. So I trimmed it to the well-known range plus the registered ports that actually turn up in real infrastructure. Keeps this a quick reference instead of a wall of noise nobody reads. When you genuinely need the obscure stuff, the IANA Service Name and Transport Protocol Port Number Registry is the canonical source. There’s a link to it below.
Sources & further reading
- IANA, Service Name and Transport Protocol Port Number Registry
- RFC 6335, Port number registry procedures (IANA/IETF)
- RFC 9293, Transmission Control Protocol (TCP)
Related tools and resources
Found your port? Good. Here’s what I’d reach for next to actually test it and lock the thing down.
