See also: What's the difference between SFTP and FTPS.

SFTP drafts and extensions

SFTP RFC specification was never finished and it's currently only available as RFC drafts. Many SFTP servers (such as OpenSSH) only supports SFTP v3 and have no intention of ever supporting v4, v5 or v6.

  • SFTP v3 - SSH File Transfer Protocol draft - supported by all modern SFTP servers
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  • SFTP v4 - not widely supported
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  • SFTP v5 - not widely supported
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  • SFTP v6 - not widely supported
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  • OpenSSH extensions and deviations - SFTP extensions implemented by the most common SSH server
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  • SFTP extensions - official but rarely-supported extensions
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SSH RFCs and extensions

SFTP almost always runs over an SSH channel.

  • RFC4250 - The Secure Shell (SSH) Protocol Assigned Numbers
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  • RFC4251 - The Secure Shell(SSH) Protocol Architecture
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  • RFC4252 - The Secure Shell (SSH) Authentication Protocol
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  • RFC4253 - The Secure Shell (SSH) Transport Layer Protocol
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  • RFC4254 - The Secure Shell (SSH) Connection Protocol
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  • RFC4255 - Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints
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  • RFC4256 - Generic Message Exchange Authentication for the Secure Shell Protocol (SSH)
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  • RFC4419 - Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol
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  • RFC4462 - Generic Security Service Application Program Interface (GSS-API) Authentication and Key Exchange for the Secure Shell (SSH) Protocol
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  • OpenSSH extensions and deviations - SSH extensions implemented by the most common SSH server
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