Port 80: HTTP

Plain web traffic. Browsers use it when an address starts with http:// and has no port.

Registry entry

What it is used for

Plain web traffic. Browsers use it when an address starts with http:// and has no port.

The risk

Everything sent over it can be read or changed on the way.

What to do

Redirect to HTTPS (443). Keep it open only for that redirect and for certificate checks that need it.

In the registry

Port 80 is a system port (0 to 1023), the range for standard services. The registry lists 3 services for this number: http (World Wide Web HTTP); www (World Wide Web HTTP); www-http (World Wide Web HTTP). Its main entry is http, "World Wide Web HTTP", registered for tcp, udp, sctp. IANA adds a note: "Defined TXT keys: u=<username> p=<password> path=<path to document>; This is a duplicate of the "http" service and should not be used for discovery purposes.; This is a duplicate of the "http" service and should not be used for discovery purposes. u=<username> p=<password> path=<path to document> (see txtrecords.html#http) Known Subtypes: _printer NOTE: The meaning of this service type, though called just "http", actually denotes something more precise than just "any data transported using HTTP". The DNS-SD service type "http" should only be used to advertise content that: * is served over HTTP, * can be displayed by "typical" web browser client software, and * is intented primarily to be viewed by a human user. Of course, the definition of "typical web browser" is subjective, and may change over time, but for practical purposes the DNS-SD service type "http" can be understood as meaning "human-readable HTML content served over HTTP". In some cases other widely-supported content types may also be appropriate, such as plain text over HTTP, or JPEG image over HTTP. Content types not intented primarily for viewing by a human user, or not widely-supported in web browsing clients, should not be advertised as DNS-SD service type "http", even if they do happen to be transported over HTTP. Such types should be advertised as their own logical service type with their own DNS-SD service type, for example, XUL (XML User Interface Language) transported over HTTP is advertised explicitly as DNS-SD service type "xul-http".".

How to find out whether it is open on your computer

On your own computer or server, ask the operating system which programs are listening for connections, and look for port 80 in the list. If a program you do not recognise listens on it, find out what it is before you close it. From outside, test only networks that you own or have permission to test: scanning other people's networks can be treated as an attack.

This is an independent guide. It is not connected with IANA, the IETF or any network equipment maker. Address and port data come from the IANA registries as fetched on 14 November 2026; RFC texts were read from rfc-editor.org. Check the originals for anything you rely on.