Fullwidth Digit One

It is the fullwidth form of ordinary 1.

Fullwidth is a layout distinction carried by a character, not a second numeric value. East Asian text systems aligned Chinese, Japanese, and Korean characters in square cells; matching wide Latin letters, digits, and punctuation let mixed text line up. In Japanese, the wide form is 全角 (zenkaku), and the narrow form is 半角 (hankaku). The character encodes a width distinction, but its displayed width still depends on font and layout.

Japan's JIS C 6226 standard for exchanging Japanese text was established in 1978. Its later JIS X 0208 standard included wide digits alongside kana, kanji, letters, and symbols. ASCII and JIS X 0201 supplied narrow forms; JIS X 0208 supplied wide forms. Encodings such as Shift_JIS and ISO-2022-JP combined them, so Unicode retained the width variants for compatibility with older text. They do not create a new numeral.

Why does a form reject １?

A strict field may require the narrow ASCII digit 1.

Fullwidth １ and narrow 1 represent the same number but are separate characters. If a field says 半角 (hankaku, halfwidth), enter 1; if it says 全角 (zenkaku, fullwidth), enter １.

Tokyo's government digital service guide for form design, issued in March 2026, recommends accepting both widths and converting common email, phone, postal, and address fields. A form that rejects one width applies a validation rule. Unicode's NFKC compatibility normalization converts １ to 1; NFC canonical normalization leaves this width distinction intact. Use NFKC only when the original width is not needed.