FTP Error 503 Login Authentication Failed

Welcome to CoreNetworkZ Tech Solutions. Today, I will explain one FTP error message- 503 Login Authentication Failed, and the quick fix.

Yesterday, while trying to access my web hosting account, I received an error message 503 Login Authentication Failed.

I have been using FireFTP as my FTP client for one year and never faced such an issue. I had been using FileZilla before migrating to FireFTP, but it never showed such a problem. However, I do not believe it is an issue with FireFTP.

I checked the username, password, and host address, but they were correct. I tried to log in to the web host account a few more times but received the same error.

The new popup was "503 Login error". This tutorial explains the reasons and the solution for "503 Login Authentication Failed". Since I was in a hurry, I couldn't troubleshoot the issue yesterday. I deleted the entire FTP cache and manually entered the FTP server access details. This time, I didn't face any trouble accessing the web server.

Rajiv Adatia asked me in the comments if I could share the screenshot. Luckily, I saved the screenshot of the popup I received.

Amit Pawan and John Berg asked for reasons for this FTP error. Just like Amit, I also was curious.

So, I started searching for more about this message. In many discussion forums, experts say "503 Login Authentication Failed" is due to the incorrect username or password.

You may get an alert if the host address is wrong. Another possibility is the usage of Caps Lock without knowing that the key is on while entering the username and password. Anyway, after clearing the cache of my FTP program (deleting previously saved username, password, and host address), I successfully logged in to my server ftp account.

Julia Bedell and William Smith asked for a solution to fix this FTP error while establishing a connection between the web server and the computer.

The reason for 503 Login Authentication Failed: An FTP error occurred - cannot make connection to host is the incorrect File Transfer Protocol login information.

Now, let us check the solution.

• Port Number should be 21 (the FTP server uses port number 21 to transfer files).

  
  

• The host address, FTP username, and password should be correct.

  
  

• Make sure to turn off the Caps Lock.

  
  

• If the problem is still not fixed, clear the cache.

PS: Clearing the cache means deleting all stored FireFTP usernames, passwords, and host addresses. You have to back up the necessary details you entered.

1. https://forum.filezilla-project.org/viewtopic.php?t=24336
2. https://superuser.com/questions/809826/ftp-cannot-connect-using-filezilla-on-windows-503-failure-of-data-connection