Overview

During an uncontrolled bout of nostalgia, I thought it might be fun to see what the state of IRC is these days.

I couldn't find a macOS client that I liked, so I built this one.

It's 100% free and open source. Contributions welcome, throw up a PR (assuming it broadly aligns with the goals below). If changing something graphical, include a screenshot showing what the change is/does. Similarly, feel free to open an issue here for bug reports/feature requests.

Design Principals

Some thoughts/goals I had while making this.

• macOS Native app - easily installable via the App Store
• Open source - I think thats important for a chat app
• Tasteful (but opinionated) UI, following modern SwiftUI UI/UX guidelines
  • Sixteen themes, including clean light/dark modes, GitHub and Catppuccin variations, Everforest Light, Gruvbox Dark, Lobster, Nord, Rose Pine, Solarized Sepia, Cyberpunk, Greyscale, and a C64-inspired palette :-)
• Generally lightweight. I'm basically just adding features I need/find useful as I go rather than overloading with every possible thing one could do
• Accessibility baked in from day one - the app should work well with Voiceover, etc
• Profiled and optimized for low resource use
  • While connected to 7 active servers / 25 channels, memory footprint remained <150MB
• No telemetry, no phone-home, no ads, no in-app-purchases, no junk
• Secure-by-default, where possible. Prefers TLS. Option to easily connect via an SSH tunnel
  • SSH is nice, as many IRC servers reveal the IP address you're connecting from
• No DCC/filesharing features. I'm just not interested in it, but maybe will add support for it at some point
• Client-side ignoring for people, plus persistent muting for channels and direct messages
• I probably won't add scripting, it's not something I find useful, and would add a ton of complexity/increased risk of security issues. That said, there is basic "run these commands on connect" support already

SSH tunneling

Each server profile can route its IRC connection through an SSH server. Enable Connect through an SSH tunnel while adding or editing a profile, then enter the SSH host, port, and username. Password authentication and unencrypted OpenSSH private keys are supported; secrets are stored in the macOS Keychain. Ed25519 keys are recommended. RSA keys currently work only with SSH servers that still permit legacy ssh-rsa signatures; many modern servers require RSA-SHA2, so use Ed25519 or password authentication with those servers.

Netsplit learns the SSH host key on the first connection and pins it to that server profile. A changed key is rejected until you explicitly forget the saved host identity. IRC TLS, when enabled, remains end-to-end inside the SSH tunnel.

On-connect commands

Each server profile can run two ordered lists of commands after registration. The pre-join phase is useful for identifying with NickServ or performing other account setup before protected channels are joined. The post-join phase runs after retained and favorite channel join attempts complete, making it suitable for ChanServ requests, modes, topics, and other channel setup. Client commands such as /msg NickServ IDENTIFY ... and raw IRC commands are both accepted. Both command lists are stored in the macOS Keychain because they may contain passwords.

Commands are sent 0.5 seconds apart. Netsplit waits 2 seconds after the final pre-join command before joining channels. Post-join commands begin after the server confirms or rejects each automatic join attempt, with a 20-second fallback for servers that leave a join request unanswered.

Keyboard shortcuts

Netsplit is designed to be usable without a mouse. These shortcuts are also listed in the app menus where applicable.

Shortcut	Action
⌘K	Open the jump palette to search active servers, channels, and direct messages.
⌘1–⌘9	Switch to an active server in sidebar order, restoring its last-open conversation.
⌘[ / ⌘←	Navigate back through recently viewed conversations.
⌘] / ⌘→	Navigate forward through recently viewed conversations.
⌃⌘S	Move keyboard focus to the server and channel sidebar.
⌃⌘M	Move keyboard focus to the message field.
⌘L	Browse channels on the selected server.
⌘W	Close the current conversation, leave the current channel, or disconnect the selected server.
⌘E	Show or hide the server and channel sidebar.
⌘B	Show or hide the channel member list.
⌘+ / ⌘-	Increase or decrease transcript text size.
⌘0	Restore the default transcript text size.

While the jump palette is open, type any part of a server, channel, or nickname; use ↑ and ↓ to choose a result, Return to open it, or Escape to close the palette.

Development and tests

Open Netsplit/Netsplit.xcodeproj and use the shared Netsplit scheme. Its normal Run action (Command-R) builds and launches the app. Test (Command-U) runs the focused regression suite using the shared NetsplitCore test plan.

Supported commands

Commands are entered in the message field with a leading /. Netsplit sends commands to the server associated with the current conversation, so select a server, channel, or private message first.

Messaging

Command	Description
/msg <nickname> <message>	Send a private message.
/query <nickname> <message>	Send a private message and open that conversation.
/notice <target> <message>	Send a notice to a nickname or channel. Incoming notices are displayed too.
/me <action>	Send a CTCP ACTION message to the current channel or private message.
/slap <nickname>	Send the classic trout-slap action to the current channel or private message.
/ping <nickname>	Ping another user via CTCP and report the round-trip time.

Channels and connections

Command	Description
/join <channel>	Join a channel. A missing channel prefix is automatically changed to #.
/hop [#channel] [message]	Leave and immediately rejoin the current channel or a named joined channel, optionally with a part message.
/list [arguments]	Open the live channel browser and request the server's channel list.
/part [#channel] [reason]	Leave the current channel, a named joined channel, or include a part reason.
/server <hostname> [port] [--tls|--no-tls]	Connect for this session without saving a profile. With no port, the defaults are 6697/TLS or 6667 with --no-tls. Explicit port 6697 implies TLS; other explicit ports imply plaintext unless overridden by a flag.
/disconnect [reason]	Disconnect from the current server.
/quit [reason]	Disconnect from the current server.
/topic [#channel] [topic]	View or change a topic. In a channel, a non-channel first argument is treated as the new topic.

Identity and information

Command	Description
/nick <nickname>	Change your nickname.
/whois <nickname>	Look up a user's IRC information.
/who <channel-or-nickname>	Request a WHO listing.
/motd [server]	Request the server's message of the day.
/version [nickname]	With no nickname, request the server version; with one, request that user's client version via CTCP.
/ctcp <nickname> version	Alias for a CTCP client-version request.

Modes and moderation

These commands require the appropriate server or channel privileges.

Command	Description
/mode <nickname> <flags>	View or change user modes.
/mode <#channel> <flags> [arguments]	View or change channel modes.
/op [#channel] <nickname>	Give channel operator status. Defaults to the current channel.
/deop [#channel] <nickname>	Remove channel operator status. Defaults to the current channel.
/voice [#channel] <nickname>	Give voice status. Defaults to the current channel.
/devoice [#channel] <nickname>	Remove voice status. Defaults to the current channel.
/ban <mask> [#channel] [reason]	Set a custom ban mask, then kick matching members after the server confirms it. Defaults to the current channel.
/invite <nickname> <#channel>	Invite a user to a channel.
/kick [#channel] <nickname> [reason]	Remove a user from a channel. Defaults to the current channel.
/kill <nickname> <reason>	Disconnect a user from the network (IRC operator only).

Local controls

Command	Description
/clear	Clear the transcript for the selected server, channel, or private message.
/ignore <nickname>	Hide messages and notices from a nickname on the current network.
/unignore <nickname>	Restore messages and notices from a nickname on the current network.
/showignores	List ignored nicknames for the current network.
/mute	Mute unread highlighting and notifications for the selected channel or direct message.
/unmute	Restore unread highlighting and notifications for the selected conversation.
/showmutes	List muted conversations for the current network.

/away and /names are also sent directly to the current server. Any other unrecognised slash command is passed through unchanged, for networks that support additional IRC commands.