Multiaddress

Multiaddress is a self-describing addressing format used in modern decentralized networks, notably libp2p and IPFS. It encodes network endpoints as a sequence of protocol elements, allowing a single address to describe how to reach a host over different transport layers.

A multiaddress consists of one or more protocol components written as a slash-delimited string. Each component begins with a protocol name and may be followed by a value, such as an IP address or port. For example, /ip4/127.0.0.1/tcp/4001 represents localhost reachable over TCP port 4001. Another example, /dns4/example.com/tcp/443, points to a domain name resolved to an IP and then to port 443. The textual form can be parsed without external context and the same address may be translated to a binary encoding used by software libraries.

Multiaddresses are defined by a protocol registry. Protocols can be extended through new codes, allowing additional transport layers and addressing schemes to be added without changing existing addresses. Some protocols carry values (IP addresses, ports, paths) while others are simple flags. A multiaddress can also embed a peer identifier, such as /p2p/<PeerID>, enabling direct addressing of a specific node in a network.

In practice, nodes advertise and exchange multiaddresses to enable dialers to connect, regardless of the underlying transport. The approach supports mix-and-match of IPv4, IPv6, DNS, UNIX sockets, and application-layer protocols, while remaining portable across networks and implementations.

Libraries exist in multiple languages to parse, serialize, and manipulate multiaddresses, making it a foundational component of multi-protocol networking stacks like libp2p.