Japanese character converter: fullwidth, halfwidth, hiragana & katakana
Switch character width or kana without changing the rest of your text.
Runs in your browser. Your text is not uploaded or stored. Up to 20,000 characters per conversion. Open a TXT or paste text. TXT downloads use UTF-8.
全角・半角変換、ひらがな・カタカナ変換
英字・数字・スペース・カナから、変換する文字を選べます。例：ＡＢＣ１２３ → ABC123、ｶﾀｶﾅ → カタカナ。入力した文章はサーバーに送信されません。
How to use this converter
For forms and office systems, choose exactly which character groups need a width change. Example: ＡＢＣ１２３ → ABC123. To expand halfwidth kana, choose Halfwidth → Fullwidth: ｶﾀｶﾅ → カタカナ. To change the script, choose a hiragana/katakana direction: ひらがな → ヒラガナ.
Select letters, numbers, spaces, kana and ASCII symbols separately for width conversion. Voiced and semi-voiced halfwidth kana are combined correctly: ｶﾞ → ガ and ﾊﾟ → パ. Kana punctuation (｡｢｣､･) is included with kana. Hiragana/katakana modes affect kana only. Choose Hiragana → Halfwidth kana for bank and office forms.
Conversion limits & mixed text
Kana conversion is not kanji reading, romaji transliteration or translation. Characters without a halfwidth equivalent stay unchanged, including small ヵ/ヶ. ASCII punctuation such as ！ or ： is converted only when Symbols is selected. Yen signs and wave dashes are preserved. Circled numbers, mathematical characters, Latin accents and unrelated scripts are preserved. Combining kana marks can be canonically composed.
Plain text only: rich text, font metadata and document layout are not imported. No font is included or required for Unicode output beyond your device’s normal script support.
Open-source engine & licences
Width mappings follow Unicode character ranges and targeted normalization; no whole-document NFKC. Upstream source. Licence notices and downloadable source.