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Half-width → full-width (Japanese)
Convert half-width katakana, ASCII, numbers, and symbols to full-width characters with a frontend tool.
Japanese half-width to full-width
About half-width and full-width in Japanese
What the difference is
Japanese text often has two forms of the same character: half-width, occupying one cell (ABC, 123, ｱｲｳ), and full-width, occupying two (ＡＢＣ, １２３, アイウ). They look alike but sit at different Unicode code points, so software treats them as completely different strings.
Half-width katakana (ﾊﾝｶｸ) causes the most trouble. It survives from early terminal and fax encodings and is generally not accepted in modern Japanese text — form validation frequently rejects it, and imports can mangle or truncate it.
When you need to convert
Japanese government and financial forms — municipal applications, opening a bank or credit card account, résumés, insurance and pension paperwork — commonly require names, addresses and phone numbers in full-width characters.
Conversely, email addresses, URLs and, in some systems, username and password fields expect half-width; full-width characters pasted in will fail validation.
Text copied out of PDFs, scans or legacy systems also tends to mix the two. Normalising it before a CSV import or a data clean-up saves a lot of rework.
How to use this tool
Paste text into the input box and the converted result appears immediately. It works in both directions — half-width to full-width and back — and lets you choose independently whether alphanumerics, symbols and katakana are included. Conversion happens entirely in your browser; the text is never uploaded.
Frequently asked questions
What is the difference between half-width and full-width?
Half-width occupies one cell (ABC, 123, ｱｲｳ) and full-width occupies two (ＡＢＣ, １２３, アイウ). They sit at different Unicode code points, so software treats them as completely different strings even though they look alike.
Why do forms reject half-width katakana?
Half-width katakana (ﾊﾝｶｸ) survives from early terminal and fax encodings and is generally not accepted in modern Japanese text. Form validation frequently rejects it and imports can mangle or truncate it.
Should names, addresses and emails be full-width or half-width on Japanese forms?
Government and financial forms commonly require names, addresses and phone numbers in full-width, while email addresses, URLs and some account or password fields expect half-width. Requirements vary, so follow the notes printed on the form.
Is the text I paste uploaded to a server?
No. Conversion happens entirely in your browser.
Requirements vary between institutions, and some forms have separate rules for long-vowel marks or voiced-sound marks. Always follow the notes printed on the form you are submitting.