IRC: 1988 Until Today

IRC (Internet Relay Chat, RFC 1459 originally, updated by RFC 2812) was the first widely-adopted internet chat protocol.

Architecture: clients connect to servers; servers are interconnected (forming a network); messages route between servers to all relevant clients.

Client A          Server 1 ←──→ Server 2          Client D
Client B    ←→    (channel #foo)                  Client E    ←→
Client C                                          Client F

Famous networks: Freenode (RIP, replaced by Libera.Chat), EFnet, Undernet, IRCnet, OFTC, Rizon. Modern open-source projects often have IRC + Matrix bridges.

The protocol is text. Each line ends with \r\n. A typical session:

S: :irc.example.com NOTICE * :*** Looking up your hostname...
C: NICK alice
C: USER alice 0 * :Alice Smith
S: :irc.example.com 001 alice :Welcome to the IRC Network alice
S: :irc.example.com 002 alice :Your host is...
S: :irc.example.com 003 alice :This server was created...
S: :irc.example.com 005 alice CHANTYPES=# PREFIX=(ov)@+ :are supported
C: JOIN #general
S: :[email protected] JOIN :#general
S: :irc.example.com 332 alice #general :Welcome to #general
S: :irc.example.com 353 alice = #general :alice @bob carol
C: PRIVMSG #general :Hello everyone
S: :alice!~alice@host JOIN #general

Compared to modern chat (Slack, Discord):

• IRC: text-only, ephemeral by default, federated, simple.
• Slack/Discord: rich content, persistent history, monolithic.
• IRC's beauty: clients are small (kilobytes), proxied easily, scriptable.
• Cost: no native E2E encryption, fragile against modern attacks, weak identity.

Modern alternatives that picked up where IRC left off:

• Matrix: federated, E2E-encrypted, rich.
• XMPP: federated, extensible, less popular today.
• IRC+SASL+TLS still used for OSS communities (oftc.net, libera.chat).