ASCII vs Binary

FTP, being a legacy protocol, offers a built in facility for converting line endings on text files between LF format and CRLF format. CRLF is most commonly used by Windows applications, while LF is most commonly used by UNIX/Linux/macOS based applications.

The FTP Protocol and many FTP clients call this setting "ASCII Mode". When ASCII Mode is enabled, files with lines ending in CRLF format will be converted to LF format when uploaded to Files.com, and LF format will be converted to CRLF format when downloaded from Files.com. ASCII mode should only be used when sending plain text files whose end-of-line (EOL) characters need to be converted for the receiving system. Examples of plain text files include TXT and CSV file types. ASCII mode behavior is almost always undesirable, and we recommend not using it unless you require EOL conversion. Sending a binary format file via ASCII mode will corrupt the transmitted file.

In nearly all use cases, you should use the "Binary mode" setting in your FTP clients, which will tell the FTP files never to make changes to the file. In binary mode, the transmitted file is always received unmodified. Binary mode should be used for all file types, including PDF, Microsoft Office, text, image, video, audio, database, application, and ZIP type files.

Files.com also offers a setting for FTP mode behavior that will neutralize the ASCII setting and tell our server to ignore it even if provided. This emulates the behavior of the built in FTP server software that is included with most Microsoft Windows Server releases. This setting may be required if you are migrating certain legacy applications or dealing with customers where you aren't able to effectively control how they've set the ASCII/Binary setting.