What Conn supports

Devices

• iPhone, iPad and Mac, in one purchase. The App Store offers Conn from iOS and iPadOS 17 and macOS 14; we test on 26 and 27, and recommend them.
• iPhone Duo, including its folded laptop layout.
• Where a device has no Secure Enclave, new keys are Ed25519 and kept in the Keychain.

SSH

Conn's SSH is built on Apple's SwiftNIO SSH, with patches of Conn's own.

Part	What Conn uses
Key exchange	curve25519-sha256 (offered first), curve25519-sha256@libssh.org, ecdh-sha2-nistp384, ecdh-sha2-nistp256, ecdh-sha2-nistp521
Ciphers	aes256-gcm@openssh.com, aes128-gcm@openssh.com
MACs	None needed: both ciphers carry their own integrity check. From 1.2, a server that allows only encrypt-then-MAC MACs doesn't stop Conn connecting.
Server (host) keys	ssh-ed25519, ecdsa-sha2-nistp256, -nistp384, -nistp521
Sign in	Password, and public key
Your keys	Ed25519; ECDSA P-256, P-384 and P-521; P-256 in the Secure Enclave
Key files	OpenSSH (unencrypted), PEM SEC1 and PKCS#8 ECDSA
Jump hosts	Chains, like ProxyJump; one-machine ProxyJump from an SSH config (1.2.1)
Port forwards	Local forwards, like ssh -L (1.2.1)
Terminal	xterm-256color, 10,000 lines of scrollback
tmux	2.1 or later
Timeouts	10 seconds to connect, 20 to set up; a silent terminal link is noticed in 5 to 10 seconds

Files (SFTP)

• SFTP version 3, which is what OpenSSH uses.
• Safe saves and renames that replace a file use OpenSSH's posix-rename@openssh.com; without it, files open read only. Saves are flushed with fsync@openssh.com where the server offers it.
• The editor and previews take files up to 1 MiB; the editor edits UTF-8 text.
• Up to 200,000 items in one folder.

Screen (VNC)

Part	What Conn supports
Protocol	RFB 3.3, 3.7 and 3.8, and Apple's own 3.889
Sign in	Apple's Screen Sharing with a Mac account; RSA-AES (as a Raspberry Pi's WayVNC and TigerVNC use) with an account or a password; a VNC password; none
Encryption	RSA-AES that encrypts the whole session counts as encrypted. Kinds that encrypt only the sign in show an open padlock. Or over SSH, or Tailscale.
Encodings	Tight (with JPEG), ZRLE, zlib, Hextile, CopyRect and Raw
Extras	Server cursors, resizing, several displays (ExtendedDesktopSize, and Apple's own on a Mac), and Extended Clipboard
Colour	32-bit true colour
Size	Up to 16,384 pixels on a side, and 64 million pixels, less on devices with little memory
Screen keys	RSA, 2048 to 4096 bits

Networks

• IPv4 and IPv6 addresses, and names, including .local names and Tailscale MagicDNS names.
• Your local network (with Local Network permission), any VPN, Tailscale (which Conn recognises and proves), jump hosts, and public addresses.
• Discovery finds machines that announce SSH, SFTP or screen sharing over Bonjour.

Tested with

Tested 17 September to 5 October 2026:

• Mac, macOS 26.7: Screen (Screen Sharing) and Terminal (Remote Login)
• Mac, macOS 27.0: Screen
• Raspberry Pi 4, Raspberry Pi OS (Debian 13): Screen with its own WayVNC 0.10.1, and Terminal
• Debian 12: Terminal and Files with OpenSSH, Screen with TigerVNC 1.12
• Debian 13: Screen with TigerVNC 1.15, x11vnc 0.9.17 and TightVNC 1.3.10

Everything else is untested, including Files on a Mac or a Raspberry Pi, other macOS versions and VNC servers on Windows. They may well work; if you try one, we'd like to hear.

Not supported yet

Not supported	Instead
RSA keys, and servers with only an RSA host key	Use an Ed25519 or ECDSA key; most servers have an Ed25519 host key too.
Keyboard-interactive and two-factor sign in	Allow a password or a key for the account.
Key files with a passphrase, PuTTY .ppk files	Make a new key, or convert the file. See Adding a key.
Host certificates	The machine's plain host key.
SOCKS (-D) and remote (-R) forwards, agent forwarding, X11 forwarding	Local forwards and jump hosts.
Mosh	tmux, which keeps sessions running through a dropped link.
Search in the terminal	tmux's own search, or grep.
VNC servers that require VeNCrypt or TLS	Turn on password or RSA-AES sign in, and use SSH or Tailscale for privacy.
RDP (Windows Remote Desktop)	A VNC server, though VNC on Windows is untested.
Moving files between folders, folder transfers	A terminal.
Push notifications	Needs you, while Conn is open; on a Mac, notifications while Conn runs.
Android	Conn is for iPhone, iPad and Mac.