FTP Reply Code Structure
FTP reply codes are three-digit numbers, similar to HTTP and SMTP. The first digit indicates the type of response.
1xx — Preliminary Reply
The command was accepted but requires another command to complete.
- 150 — File status okay, about to open data connection
2xx — Completion Reply
The requested action was completed.
- 200 — Command OK
- 220 — Service ready for new user (connection greeting)
- 226 — Closing data connection, transfer complete
- 230 — User logged in, proceed
- 250 — Requested file action okay
- 257 — Directory created / current directory
3xx — Intermediate Reply
More information is needed.
- 331 — Username OK, need password
- 350 — Requested file action pending, send RNTO
4xx — Transient Negative
Temporary failure, try again later.
- 421 — Service not available, closing control connection
- 425 — Can't open data connection
- 426 — Connection closed, transfer aborted
- 450 — File unavailable (busy/locked)
5xx — Permanent Negative
The command failed permanently.
- 500 — Syntax error, command unrecognized
- 530 — Not logged in
- 550 — File not found or permission denied
- 553 — File name not allowed
Active vs Passive Mode
425 errors are often caused by firewall issues with FTP data connections. Switching from active to passive mode (PASV) usually resolves these.