- Port
- 53
- Protocol used by the service
- TCP/UDP
- Encryption
- Unencrypted
- IANA description
- Domain Name Server
- IANA service name
- domain
What port 53 is used for
Domain name resolution — translating hostnames to IP addresses. UDP is used for most ordinary queries; TCP is used for larger responses (like DNSSEC-signed records) and zone transfers.
Is port 53 encrypted?
Classic DNS on port 53 is unencrypted. Newer alternatives — DNS-over-HTTPS (port 443) and DNS-over-TLS (port 853) — encrypt the query itself.
Firewall & exposure considerations
A DNS resolver open to the public internet on UDP/53 without query restrictions can be abused as part of DNS amplification DDoS attacks — this is one of the most common attack vectors involving this port. Recursive resolvers should restrict which clients can query them.
Related ports
References
- RFC 1035 — Domain Names, Implementation and Specification
- RFC 7766 — DNS Transport over TCP
- IANA registration for port 53
Look up any other port
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Last reviewed: . Data source: IANA Service Name and Transport Protocol Port Number Registry. Security and usage notes are this site's own editorial content, not official IANA data.