Port 853DNS over TLS

Encrypted DNS resolution using TLS, conventionally on TCP port 853.

transport: tcp · udp
in transit: encrypted
assignment: official
risk: 3/10
lookups: 0

Technical Details

what runs on :853

DoT runs DNS over a TLS connection, normally using TCP, with the TLS handshake preceding DNS queries. Each DNS message is framed with a two-byte length field, as specified for DNS over TCP, and the default TLS service is port 853. Plain DNS generally uses port 53, while DNS over HTTPS uses port 443; RFC 8094 defines DNS over DTLS for UDP 853.

Security Information

exposure of :853

risk score

3/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

security averages 3.3 across 294 ports — this one sits 0.3 below.

in transit

encrypted

payloads are protected on the wire

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

TLS encrypts DNS contents and provides server authentication when certificate validation is used, but the resolver can still observe queries and clients can expose connection metadata. Publicly reachable recursive resolvers should be access-controlled or deliberately operated as public services, because open resolvers can be abused for query load and DNS-related denial-of-service activity.

Record

iana registry entry

port: :853
service: DNS over TLS
transport: TCPUDP
encryption: tls / encrypted
assignment: iana registered
risk: 3/10caution
category: Security Network Services
usage: Port 853 is used by DNS clients to reach recursive resolvers over DNS over TLS (DoT). It is commonly configured by operating systems, browsers, enterprise resolvers, and public DNS providers; DNS over DTLS is also defined for UDP 853 but is less common.
lookups: 0rank 994
added: 2026-09-09
updated: 2026-09-09
references: IANA Service Name and Transport Protocol Port Number Registry
RFC 7858: Specification for DNS over Transport Layer Security (TLS)
RFC 8094: DNS over Datagram Transport Layer Security (DTLS)

Something wrong?

This record is maintained by the engineers who use port 853. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-09-09.

01edit any field on a page of its own
02a model checks it for accuracy and spam
03clean and confident goes live immediately

edit this record →back to the registry

Related Ports

all 294 in security →

the 8 most looked-up other ports in security — 294 ports carry that label.

port	service	proto	category	risk	views
:8881	Atlasz Secure Server	TCP	Web Services	caution	67.6k
:443	HTTPS	TCPtls	Web Services	caution	65.9k
:8291	Winbox MikroTik Admin	TCP	Security	caution	62.9k
:3268	Microsoft Global Catalog (GC)	TCPUDP	Security	caution	54.6k
:135	Microsoft EPMAP	TCPUDP	Security	caution	51.9k
:3128	Squid Proxy HTTP	TCP	Web Services	caution	45.8k
:8080	HTTP Alternate	TCPtls	Web Services	caution	44.9k
:7000	Vuze HTTPS Tracker	TCPtls	Security	caution	28.9k

risk mix of the 8 listed

caution100%

3 of 8 encrypted

Port :853DNS over TLS

Technical Details

Security Information

Related Ports

Port 853DNS over TLS