500
FTP
500 Syntax Error
Syntax error, command unrecognized. The server could not parse the command. This may also be sent when the command line is too long.
On this page
When You See This Code
When you send a malformed or misspelled command, or a command the server does not recognize at all.
How to Fix
Check the command spelling and syntax. Use HELP to see the list of supported commands on this server.
Specification
Compare With
Guides
FTP Reply Codes: Understanding File Transfer Responses
DNS & Networking
TCP Three-Way Handshake and Connection Lifecycle
DNS & Networking
Essential Network Debugging Tools: ping, traceroute, mtr, and tcpdump
DNS & Networking
RFC 959: FTP Protocol Deep Dive
Protocol Deep Dives
TLS 1.3: Faster, Simpler, More Secure
Protocol Deep Dives
Migrating from FTP to SFTP: A Complete Transition Guide
Migration & Upgrades
HTTP Access Log Management: Rotation, Parsing, and Analysis
Production Infrastructure
Specifications
Glossary
Status Code
TLS Handshake
TCP/IP
Three-Way Handshake
Port Number
Firewall
Proxy Server (Forward Proxy)
Socket
Request-Response Model
RFC (Request for Comments)
Connection-Oriented
Half-Duplex
Text vs Binary Protocol
FTP Active Mode
FTP Passive Mode
FTP Control Channel
FTP Data Channel
SFTP (SSH File Transfer Protocol)
FTPS (FTP Secure)
FTP Reply Code
FTP Anonymous Access
FTP Transfer Mode (ASCII vs Binary)
FTP Resume (REST Command)
SCP (Secure Copy Protocol)
FTP Chroot Jail
WebDAV (Web Distributed Authoring and Versioning)
rsync
FTP MLSD (Machine-Readable Listing)
FTP NAT Traversal
Transfer Integrity
FTP over TLS (RFC 4217)
File Locking
Bandwidth Throttling
TLS Versions
Frequently Asked Questions
What is FTP 500 Syntax Error?
Syntax error, command unrecognized. The server could not parse the command. This may also be sent when the command line is too long.
When do you see FTP 500 Syntax Error?
When you send a malformed or misspelled command, or a command the server does not recognize at all.
How to fix FTP 500 Syntax Error?
Check the command spelling and syntax. Use HELP to see the list of supported commands on this server.