Half-width to Full-width: Layout and Form Input

When you actually need it

Application forms, resumes, and bank transfer details in Japan commonly ask for full-width input. Converting a half-width name or number is what gets it past the validation, and for Japanese typesetting, mixing widths makes the spacing look uneven.

Unifying an old document is the other case: one file uses full-width in some places and half-width in others, so the text looks inconsistent. Converting to full-width and pairing it with a Japanese font gives a more conventional result.

• Japanese forms that require full-width input
• Even visual width in mixed text
• Mixed widths in old documents

What changes, and what it costs

The conversion covers printable ASCII from 0x21 to 0x7E, adding 0xFEE0 to each: A becomes Ａ, 1 becomes １, ! becomes ！. Chinese characters and kana are outside the range, and so are the Japanese 、 and 。 marks.

Every space becomes the ideographic space U+3000, including the spaces between English words. Hello World turns into Ｈｅｌｌｏ　Ｗｏｒｌｄ with visibly wide gaps. Code indentation, URLs, and email addresses deform along with it and usually stop working. Full-width glyphs are wider, so button and table text can overflow.

• Printable ASCII shifts up by 0xFEE0
• Every space becomes U+3000
• Wider glyphs can overflow tight layouts

Alternatives and when not to use it

When only the digits need to be full-width, many forms and input methods do the conversion themselves, which is safer than converting a whole passage. Japanese layout usually wants full-width digits and letters with separate rules for punctuation, so check the requirement first.

For the reverse problem, full-width digits breaking a script, use the full-width to half-width converter. Neither direction reads context, so back up before working on code, passwords, or links. Check the output character by character afterwards.