FTP Drive Icon


Settings are specific to service providers. Use the provided connection profiles.


Connection profiles can be installed from Preferences → Profiles..


If you have access to a server using a secure shell (SSH2), most probably sftp-server is also installed and configured and you can connect using SFTP.

OpenSSH Configuration Interoperability

Public Key Fingerprints

Public key fingerprints are checked against and written to ~/ssh/known_hosts when accepted. This does not apply to the Mac App Store version which does store key fingerprints in the preferences.

Configuration File

The following configuration options from ~/.ssh/config are supported for SFTP connections:

  • IdentityFile for public key authentication.

  • IdentityAgent for public key authentication. Specifies the UNIX-domain socket used to communicate with the authentication agent.

  • HostName aliases.

  • User preference for login credentials.

  • ProxyJump to connect via SSH tunnel through bastion server.

  • PreferredAuthentications to limit authentication methods tried to login.

  • IdentitiesOnly. Only try explicitly set private keys to authenticate but not all identities found in SSH agent. Resolves Too many authentication failures errors with servers limiting the number of attempted authentication requests.

  • A bookmark will update its public key authentication setting from the IdentityFile configuration in ~/.ssh/config. Also when opening a new connection using File → Open Connection…, IdentityFile and User parameters in the OpenSSH user config file are auto completed.

Example ~/.ssh/config configuration:

Host myhostname
	User myusername
	IdentityFile ~/.ssh/mykey-rsa

To use the same key for all hosts add a wildcard entry such as

Host *
	IdentityFile ~/.ssh/mykey-rsa

which is then used when configuring a new bookmark.


If you have a configuration in your ~/.ssh/config make sure to specify the Host alias as hostname in your bookmark configuration. This is important for cases the Host alias is different from the HostName:

Host myhostalias
	HostName myverylonghostname.example.com
	User myusername
	IdentityFile ~/.ssh/mykey-rsa.pub

For the configuration above the hostname to specify in your bookmark is myhostalias.

Default Public Key Authentication Keys

You can enable the use of a default set of keys ~/.ssh/id_rsa and ~/.ssh/id_dsa (in this order) by setting the hidden configuration option ssh.authentication.publickey.default.enable to true.

defaults write ch.sudo.cyberduck ssh.authentication.publickey.default.enable true

Public Key Authentication

Public-key authentication allows you to connect to a remote server without sending your password over the Internet. Public-key authentication uses two keys:

  1. a private key that only you have that should be kept in a secure place and protected with a password

  2. the public key, which is placed on the server you wish to gain access to, usually by the system administrator when your account is set up.

Private keys can be configured in the Bookmark or Connection panel.

PuTTY Key Format Interoperability

PuTTY private keys (.ppk) are supported for rsa key types. ed25519 is not supported.

OpenSSH Key Format Interoperability

OpenSSH private keys of type rsa, dsa, ecdsa and ed25519 (in OpenSSL PEM format) are supported. The new OpenSSH format (openssh-key-v1) is only supported for ecdsa and ed25519.

Configure Public Key Authentication

  1. Run the command ssh-keygen from the Terminal.app (macOS) or console (Windows) to generate a public/private pair of keys. They will be put in your directory ~/.ssh, though you will probably be asked to approve or change this location. When you generate the keys you will be asked for a ‘passphrase’. If you use a passphrase then you will have to enter it each time you use the keys for authentication. That is, you will have to type in the passphrase every time you log in, just as you would with a password. If you don’t enter a passphrase (just press the return key) then you will be allowed to log in without having to enter a passphrase. This can be more convenient, but it is less secure.

    ssh-keygen -m PEM -t rsa
  2. Copy the public key to the remote host you wish to access and add it to the file authorized_keys in your ~/.ssh directory. (If that file does not exist then you should create it.) Anybody listed in the authorized_keys file (via their public key) is allowed to log-in, provided that they can prove that they possess the corresponding private key. Thus, if you have the private key in your .ssh directory on your home machine you’ll be allowed in.

    ssh hostname < ~/.ssh/id_rsa.pub 'cat >> .ssh/authorized_keys'
  3. In the Connection Dialog or the Bookmark editor in Cyberduck select Use Public Key Authentication and select the private key in your .ssh directory.

OpenSSH User Certificate Authentication


  • Cyberduck 8.9.0 or later required

  • Mountain Duck 4.16.0 or later required

Applies to SSH servers, which are configured with TrustedUserCAKeys, refer to your software vendor for configuration. To configure authentication with a User CA signed private key, configure the private key as described in Configure Public Key Authentication step 3. The signed public key file must reside next to the private key file, suffixed -cert.pub or .pub. The CertificateFile configuration directive in ~/.ssh/config is not supported. Pay attention to the server configuration and PubkeyAcceptedAlgorithms specifically which determines the allowed private key algorithms to authenticate with.

Public Key Authentication Using SSH Agent

When connecting to a SSH server, Cyberduck will lookup matching private keys from the SSH agent when attempting to authenticate with the server if no password is available and no explicit private key to use is configured in the bookmark.


The feature is not supported when running Cyberduck from the Mac App Store because of sandboxing restrictions.

The agent ssh-agent is running by default on macOS. You add private key identities to the authentication agent using the program ssh-add. The SSH agent is located using the IdentityAgent directive in ~/.ssh/config or if missing from the environment variable SSH_AUTH_SOCK.


When authenticating using Public Key Authentication with an SSH agent containing multiple identities, it makes sense to add IdentitiesOnly yes in ~/.ssh/config to limit authentication attempts with this identity only. Otherwise the server may deny the connection because of too many login failures and you will receive the error Too many authentication failures.

Since the private key is not always available on the filesystem, specifying a public key as IdentifyFile is also supported. This can be used to authenticate using an SSH agent backed by a hardware token containing the private key for example.

Example ~/.ssh/config configuration:

Host myhostname
	User myusername
	IdentityFile ~/.ssh/mykey-rsa.pub
	IdentitiesOnly yes

One-Time Passcodes (2FA)

Using a challenge-response authentication with one-time password generators such as DUO, SecurID or Google Authenticator is supported. After the initial login prompt for the username and password, a second login prompt is displayed to enter the one-time passcode.

Google Authenticator

A setup with a two-step verification such as Google Authenticator is supported.

Use the following configuration steps:

  1. Install libpam-google-authenticator on the server.

  2. Run google-authenticator to create a new account and scan the 2D barcode using the Authenticator application on your phone. Refer to Install Google Authenticator.

  3. Make it required for SSH logins by running echo 'auth required pam_google_authenticator.so' >> /etc/pam.d/sshd.

  4. Add ChallengeResponseAuthentication yes to /etc/ssh/sshd_config with echo 'ChallengeResponseAuthentication yes' >> /etc/ssh/sshd_config.

When logging in, enter the time-based token requested after providing username and password.

Verification Code Prompt

Verify Host Keys

Upon connecting to an SSH server for the first time, you will see a message to verify the host key uniquely identifying the server. You can ask your provider for the public fingerprint of the server to make sure you are connecting to the right host. Subsequent connections to the SSH server will make sure that the host key does not have changed to prevent spoofing attacks.

Unknown Host Key

Connect via SSH Tunnel Through Bastion Server


Cyberduck 7.7 or later required

Using the ProxyJump configuration directive in ~/.ssh/config you can connect through a tunnel. The bookmark configuration refers to the target host in the internal network. We should find a ProxyJump directive in the OpenSSH configuration ~/.ssh/config matching the hostname in the bookmark.

Sample configuration:

Host internal
	HostName server.lan
	ProxyJump user-external@jump.example.org:2222
	User user-internal

You can also work with aliases like

Host bastion-host-nickname
    HostName bastion-hostname
    User username
    Port 2222

Host remote-host-nickname
    HostName remote-hostname
    ProxyJump bastion-host-nickname

Open in Terminal

Open in Terminal allows you to open an SSH shell for the current working directory with a single click.


The feature is not supported when running Cyberduck from the Mac App Store because of sandboxing restrictions.


Use View → Customize Toolbar… to add the Terminal.app toolbar icon to your browser.


Customize SSH Command:
You can change the SSH command using the hidden configuration option

defaults write ch.sudo.cyberduck terminal.command.ssh \"ssh\ -t\ {0}\ {1}@{2}\ -p\ {3}\ \\\"cd\ {4}\ \&\&\ exec\ \\\\\$SHELL\\\"\"


  • {0} is -i <path to the private key>

  • {1} is the username from the login credentials

  • {2} is the hostname

  • {3} is the port number of the remote host

  • {4} is the current working directory in the browser

Because of all the escaping of characters, it might be easier to edit the key using Property List Editor if you have the developer tools installed. You can then set the string for the key terminal.command.ssh to ssh -t {0} {1}@{2} -p {3} "cd {4} && exec \$SHELL". Test the string in Terminal.app first if it is valid.

Using iTerm2

Version 7.4 and later:
No configuration change is required. Choose iTerm2 → Make iTerm2 Default Term and restart Cyberduck. To revert, set the default application for a file named .command to Terminal.app in Finder → Info → Open With….

Previous versions:
You can change a hidden configuration option to use a third-party terminal application instead of Terminal.app.

  • Example for iTerm2 Version 2

    defaults write ch.sudo.cyberduck terminal.bundle.identifier com.googlecode.iterm2
    defaults write ch.sudo.cyberduck terminal.command \"set\ t\ to\ \(make\ new\ terminal\)\\ntell\ t\\nset\ s\ to\ \(launch\ session\ \\\"Default\ Session\\\"\)\\ntell\ s\\nwrite\ text\ \\\"{0}\\\"\\nend\ tell\\nend\ tell\"
  • Example for iTerm2 Version 3

    defaults write ch.sudo.cyberduck terminal.bundle.identifier com.googlecode.iterm2
    defaults write ch.sudo.cyberduck terminal.command \"set\ t\ to\ \(create\ window\ with\ default\ profile\)\\ntell\ t\\nset\ s\ to\ \(current\ session\)\\ntell\ s\\nwrite\ text\ \\\"{0}\\\"\\nend\ tell\\nend\ tell\"

To reset to the default settings use:

defaults delete ch.sudo.cyberduck terminal.bundle.identifier
defaults delete ch.sudo.cyberduck terminal.command

Distribution (CDN)

You can enable custom origin Amazon CloudFront (Content Delivery Network) distribution using File → Info → Distribution (CDN).

Create and Expand ZIP or TAR Archives

The remote systems must have the archiving tools tar or zip installed respectively. Use View → Customize Toolbar… to add the Archive toolbar button to your browser window. It is not included in the default toolbar configuration.


Send custom commands and Create and expand ZIP/TAR Archives are limited to FTP and SFTP.


Select one or more files to archive in the browser. For multiple files, a file with the name Archive with the given extension of the archive format will be created.



Select one or more files to expand in the current working directory.

Remote Commands

You can send any remote command to a remote SSH server. This is for example useful if you want a HTTP server to reload its configuration or changing the ownership of files using chown on a UNIX system.


The current working directory is always your use home. Determine using pwd to get the absolute path.

Send Command


Default Protocol Handler

You can set Cyberduck or a third-party application as the default application (protocol handler) for SFTP in Preferences → SFTP. When you click URLs in another application like your web browser, this application is opened to open the URL instead.

Supported Algorithms


aes{128,192,256}-{cbc,ctr}, blowfish-{cbc,ctr}, 3des-{cbc,ctr}, twofish{128,192,256}-{cbc,ctr}, twofish-cbc, serpent{128,192,256}-{cbc,ctr}, idea-{cbc,ctr}, cast128-{cbc,ctr}, arcfour, arcfour{128,256}, aes{128,256}-gcm@openssh.com, chacha20-poly1305@openssh.com

Key Exchange

diffie-hellman-group1-sha1, diffie-hellman-group14-sha1, diffie-hellman-group14-sha256, diffie-hellman-group15-sha512, diffie-hellman-group16-sha512, diffie-hellman-group17-sha512, diffie-hellman-group18-sha512 diffie-hellman-group-exchange-sha1, diffie-hellman-group-exchange-sha256, ecdh-sha2-nistp256, ecdh-sha2-nistp384, ecdh-sha2-nistp521, curve25519-sha256@libssh.org

SSH Key Types

ssh-rsa, ssh-dss, ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521, ssh-ed25519, rsa-sha2-256, rsa-sha2-512

SSH Certificate Key Types

ssh-rsa-cert-v01@openssh.com, ssh-dss-cert-v01@openssh.com, ecdsa-sha2-nistp256-cert-v01@openssh.com, ecdsa-sha2-nistp384-cert-v01@openssh.com, ecdsa-sha2-nistp521-cert-v01@openssh.com, ssh-ed25519-cert-v01@openssh.com


Compression with zlib and zlib@openssh.com is supported.

Private Key Files

pkcs5, pkcs8, openssh-key-v1


Serv-U MFT

Serv-U MFT does not fully implement SFTPv3. Files cannot be created, renamed, uploaded as a required flag is not implemented and results in error messages.

Known Issues

Too many authentication failures

Running an SSH agent with many added identities can lead to the server error Too many authentication failures when trying to authenticate with all available identities.

  • Select the identity in the bookmark with SSH Private Key.

  • Increase the allowed authentication tries on the server by adjusting MaxAuthTries.

Possible remedies using configuration in OpenSSH configuration file:

  • IdentitiesOnly in client configuration file ~/.ssh/config. Only try to authenticate with explicitly set private key instead of all identities retrieved from SSH agent.

  • Set PreferredAuthentications in client configuration file ~/.ssh/config to disable public key authentication for example.

Illegal sftp packet length. Invalid packet: indicated length 1114795883 too large

The error message Invalid packet: indicated length 1114795883 too large may indicate you have either:

  • An echo statement in your shell init script like .bashrc. Make sure it does not output any text.

  • Interoperability issue with Globalscape EFT Server (Issue #5308).

  • Possibly the server is printing a message similar to Please login as the ubuntu user rather than root user. Please verify the username for your connection.

  • Enable SSH access on your server. Use the sftp command in a terminal to verify sftp username@domain_name. It’ll ask for your password. If you don’t have SSH access, you’ll get “Received message too long”, hence the error message.

Kex Timeout

This error can occur if you are connecting the first time to a device with a slow processor. You can raise the tmeout value in Preferences → Connection → Timeout.

Kex Timeout

Malformed known_hosts

Cyberduck refuses to connect if there are malformed entries in your known_hosts file located under ~/.ssh. Renaming this file and recreating it usually resolves this. An alternative requires manually editing the known_hosts file removing all malformed entries. Please refer to sshd(8) for a valid format.

Mountain Duck

File Permissions Reset when Saving File

Mountain Duck will forward all permission changes from Finder or any other application to the SFTP server. There is a hidden configuration option fs.setattr.chmod=false to disable the writing of permissions.

File Owner Reset When Saving File

Some editors save files using an Atomic Save feature that writes changes to a file to a temporary file later replacing the edited file by renaming the temporary file to the name of the edited file. This works well on local filesystems, where there is support to retain the owner of the file that is different from the editing user using a special function call. This does not work for volumes mounted with Mountain Duck and the file owner will be reset to the default owner for new files created on the server by the logged-in user. As a workaround, try to find a setting for the editor to disable the Atomic Save feature.

Free Space Calculation is Incorrect

The available space for a volume mounted over SFTP is determined using quota features of the SSH protocol. Technically using the space-available extension of the SFTP protocol or the statvfs@openssh.com extension from OpenSSH. If the connected device returns an invalid value (e.g. from the disk the server is running instead of the data disk) you will get an incorrect calculation for the free space. You can work around the issue using one of the following options:

  • Set a default path you want to connect to within the bookmark Path option.

  • Disable the feature in Mountain Duck by setting the hidden configuration option fs.quota.enable=false.