Alt コード

What is an Alt Code?

Alt codes are a Windows-specific method for entering special characters by holding the Alt key and typing a numeric code on the numeric keypad. Released the Alt key, and the special character appears. They were inherited from the IBM PC's original character entry system and remain functional in Windows today, providing access to hundreds of characters without requiring special keyboard layouts or IME software.

There are two varieties: the original OEM Alt codes (Alt + 1–255 based on Code Page 437, the original IBM PC encoding) and the extended Unicode Alt codes (Alt + 0xxx using the Windows-1252 or system code page).

The Two Alt Code Systems

The critical difference between Alt+0169 and Alt+169: - Alt + 169 → ® (from CP437) - Alt + 0169 → © (from Windows-1252/Unicode)

The leading zero signals to Windows: "use the ANSI code page, not OEM."

Common Alt Codes

Limitations of Alt Codes

1. Requires a numeric keypad: Laptop keyboards without Num Lock/numpad cannot use standard Alt codes. Some laptops have a Fn key override that maps letter keys to a numpad, but this is awkward.

2. Limited Unicode coverage: Standard Alt codes only reach code page characters (up to U+00FF or so). Characters beyond that range generally cannot be entered this way.

3. Application dependency: Some applications intercept the Alt key for their own menus or shortcuts and may not support Alt codes.

4. Memorization required: Unlike dead keys or Compose, Alt codes require memorizing or looking up the numeric value.

Windows Unicode Input Alternative

For broader Unicode input in Windows, type the hexadecimal code point and press Alt+X (works in Microsoft Word and some other applications):

2026 Alt+X  →  … (ellipsis, U+2026)
2014 Alt+X  →  — (em dash, U+2014)
1F600 Alt+X →  😀 (if app supports it)

This approach supports the full Unicode range, not just the first 255 characters.

Quick Facts