CP65001

CP65001 is the Windows code page number for UTF-8. In Windows terminology, a code page identifies how a byte string should be interpreted as characters. CP65001 maps to the UTF-8 encoding, making UTF-8 the Windows-identified ANSI encoding for applications that rely on code pages to convert between multibyte and wide-character representations.

In practice, CP65001 is used by certain Windows APIs and applications that operate on multibyte strings. Functions such as MultiByteToWideChar and WideCharToMultiByte can use CP65001 as the source or target encoding, enabling conversion between UTF-8 and UTF-16 (the internal Windows Unicode encoding). The current ANSI code page for a process can be queried with GetACP and changed for the console with SetConsoleCP and SetConsoleOutputCP, though changing the console code page can affect how text is rendered and interpreted.

CP65001 has historically presented compatibility challenges. Some older or poorly implemented software relied on specific non-Unicode code pages and may fail or produce incorrect results when switched to CP65001. Early Windows versions also experienced reliability issues with UTF-8 handling in certain API paths, especially in console I/O and in files or registry data that were not strictly valid UTF-8. Over time, support improved in modern Windows releases, but developers still encounter edge cases when mixing UTF-8 with legacy code paths or with non-Unicode APIs.

Best practices suggest using Unicode APIs directly where possible and treating CP65001 as a bridge for UTF-8 data rather than a primary internal encoding. When using CP65001, validate UTF-8 input, handle potential conversion errors gracefully, and be mindful of console and filesystem interactions that depend on the active code page. See also UTF-8, Unicode, and the concept of ANSI code pages in Windows.