ASCII vs Binary Transfers

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.

Automatically converting between line endings is usually controlled by a "transfer mode" or "transfer type" setting within an FTP client application. Most FTP clients allow you to choose between ASCII mode and Binary mode transfers.

Avoid ASCII Mode

When ASCII mode is enabled, files with lines ending in CRLF format are converted to LF format when uploaded to Files.com, and LF format are converted to CRLF format when downloaded from Files.com.

Only use ASCII mode for plain text files whose end-of-line (EOL) characters need to be converted for the receiving system. ASCII mode behavior is almost always undesirable because it changes the contents of the file, which corrupts files that are not plain text. We recommend not using ASCII mode unless you require EOL conversion.

Binary Mode (Recommended Default)

The "Binary mode" setting in your FTP client, which tells the FTP client never to make changes to the file, is nearly always the appropriate choice. In binary mode, the transmitted file is always received unmodified. Use binary mode for all file types to avoid making inadvertent changes to the file contents.

FTP Mode Behavior Setting

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 setting lets you switch between standard behavior and emulating the behavior of the built in FTP server software that is included with most Microsoft Windows Server releases.

Windows FTP Mode Is Not Recommended

Setting the FTP mode behavior to emulate a Microsoft Windows Server is not recommended for most of our customers, because it introduces non-standard behavior that affects all FTP connections to your site.

Only change your FTP mode behavior to emulate Windows when files are being corrupted when transferred by an FTP client, and that client cannot update its settings to select the proper transfer mode. Whenever it's possible to instead update the FTP client's settings, that is the preferred approach.