FTP return codes and SFTP status codes: the complete reference

If you run file transfers you’ll eventually stare at a numeric code and need to know what it means. There’s a trap worth clearing up first: FTP and SFTP use completely different code systems, because they’re completely different protocols. Mixing them up is the single most common source of confusion. This page covers both.

• FTP / FTPS uses 3-digit reply codes defined in RFC 959 (e.g. 226, 530, 550).
• SFTP is an SSH subsystem and uses status codes named SSH_FX_* (e.g. SSH_FX_PERMISSION_DENIED), not numeric FTP codes at all.

How FTP reply codes are structured

Every FTP reply is three digits, and each digit carries meaning.

First digit, did it work?

Code	Meaning
1xx	Positive preliminary, command accepted, another reply is coming
2xx	Positive completion, command succeeded
3xx	Positive intermediate, accepted, but waiting for more input (e.g. password)
4xx	Transient negative, failed, but try again (temporary)
5xx	Permanent negative, failed, don’t retry as-is

Second digit, what area?

Code	Area
x0x	Syntax
x1x	Information
x2x	Connections
x3x	Authentication & accounting
x4x	Unspecified
x5x	File system

So 550 reads as: permanent failure (5), file-system area (5), “your command was fine, but the file/path can’t be acted on.”

Common FTP reply codes

Code	Meaning	What it usually means in practice
110	Restart marker reply	Resuming a transfer
125	Data connection already open; transfer starting	—
150	File status OK; about to open data connection	Normal before a transfer
200	Command OK	Generic success
211	System status / help reply	Often from FEAT
213	File status	Often a file’s size or modify time
220	Service ready for new user	The greeting when you connect
221	Service closing control connection	Normal QUIT / logout
226	Closing data connection; transfer successful	Your upload/download completed
227	Entering Passive Mode	Server gave you a passive data port
229	Entering Extended Passive Mode	The IPv6-friendly EPSV form
230	User logged in, proceed	Login succeeded
234	Security mechanism accepted	FTPS AUTH TLS accepted (RFC 2228)
250	Requested file action completed	e.g. a DELE or CWD worked
257	”PATHNAME” created	Reply to MKD/PWD
331	User name OK, need password	Send PASS next
332	Need account for login	Rarely used
350	Requested action pending further information	e.g. REST before RETR
421	Service not available, closing control connection	Server shutting down or too busy
425	Can’t open data connection	Usually a passive/active mode or firewall problem
426	Connection closed; transfer aborted	The data connection dropped mid-transfer
430	Invalid username or password	Auth failed
450	File action not taken (file busy)	Temporary, retry
451	Action aborted: local error	Server-side error
452	Insufficient storage	Out of space (temporary)
500	Syntax error, command unrecognized	The server didn’t understand the command
501	Syntax error in parameters	Bad arguments
502	Command not implemented	Server doesn’t support it
503	Bad sequence of commands	e.g. PASS before USER
504	Command not implemented for that parameter	—
530	Not logged in	Authentication required or failed, the classic login error
532	Need account for storing files	—
534	Request denied, policy requires SSL	The server wants FTPS, you tried plain FTP
550	File unavailable (not found / no access)	The most common error, wrong path or permissions
551	Action aborted: page type unknown	Rare
552	Exceeded storage allocation	Quota hit
553	File name not allowed	The name violates a server rule

The two you’ll see most

• 530 Not logged in, credentials wrong, or you tried an operation before authenticating (or the server requires FTPS and you connected in plain FTP).
• 550 File unavailable, the file or directory doesn’t exist, or your account lacks permission on it. The command was valid; the target is the problem.

SFTP status codes (these are NOT FTP codes)

SFTP runs over SSH and reports results with SSH_FXP_STATUS messages carrying an SSH_FX_* code. The core set (protocol version 3, the most widely implemented) is:

Code	Name	Meaning
0	SSH_FX_OK	Success
1	SSH_FX_EOF	End of file (or no more directory entries)
2	SSH_FX_NO_SUCH_FILE	Path doesn’t exist
3	SSH_FX_PERMISSION_DENIED	Not allowed
4	SSH_FX_FAILURE	Generic failure (the catch-all)
5	SSH_FX_BAD_MESSAGE	Malformed packet
6	SSH_FX_NO_CONNECTION	No connection (client-side)
7	SSH_FX_CONNECTION_LOST	Connection lost (client-side)
8	SSH_FX_OP_UNSUPPORTED	The server doesn’t support that operation

Later protocol versions (4–6) add more specific codes, invalid handle, no such path, file already exists, write-protect, quota exceeded, and so on, but many clients and servers negotiate version 3, so the eight above are what you’ll meet most.

Why your SFTP client shows a vaguer error than FTP would

Notice SFTP has a single generic SSH_FX_FAILURE (4) where FTP has many specific 5xx codes. That’s why an SFTP “permission denied” or “failure” can feel less precise than FTP’s 550 vs 530 vs 553. It’s a protocol difference, not your client misbehaving, and it’s why a good gateway’s audit log matters: when the protocol code is generic, the server-side log is where you find what actually happened.

FTP vs SFTP vs FTPS, in one line each

• FTP, the original protocol (RFC 959). Numeric reply codes. Unencrypted.
• FTPS, FTP wrapped in TLS (RFC 4217 / 2228). Same numeric reply codes, encrypted.
• SFTP, a different protocol entirely, running over SSH. SSH_FX_* status codes, always encrypted.

If you’re choosing between them or just untangling which one you’re actually using, see the rest of our guides, including how to put SFTP in front of your own cloud storage.