Linefeeds

Linefeeds are a type of newline convention used to separate lines of text. The term commonly refers to the line feed control character, LF, which moves the cursor to the next line without returning to the start of the line. In ASCII, LF is 0x0A, and in Unicode it is U+000A. The carriage return, CR, 0x0D, returns the cursor to the beginning of the line. Some systems use CR+LF as a single newline sequence, combining both actions.

Operating systems have historically standardized on different line-ending conventions. Unix and Unix-like systems use LF as the end-of-line marker. Windows uses CRLF. Classic Mac OS used CR, but modern macOS and iOS follow the Unix convention with LF. In network protocols and many text-based formats, CRLF is often the required line terminator; for example, HTTP and SMTP specify CRLF to end lines.

In software development and data processing, line endings affect how text is stored, parsed, and displayed. Editors and integrated development environments can detect and convert line endings on read or write. Many programming languages treat the newline as a line terminator in source code, while string literals may use escape sequences like \n to represent a newline. Version control systems offer options to normalize line endings across platforms (for example, Git’s core.autocrlf setting). External tools such as dos2unix and unix2dos also perform conversions between CRLF and LF.

Problems can arise when mixed conventions are encountered in logs, source code, or data interchange, potentially causing misrendering or parsing errors. Being aware of the line-ending convention used in a given environment helps ensure text portability and consistent processing.