MojiHako

Full-width / Half-width Converter

Quickly convert between full-width and half-width characters — useful for formatting names, addresses, product listings, and form fields on Japanese websites.

Conversion mode
Send result to another tool Hiragana/Katakana Kana Pad Genko Paper

NFKC normalization also converts compatibility characters such as ① and Ⅳ. Check the result carefully if preserving the original character form matters.

How to use

  1. Paste the text you want to convert into the input box.
  2. Select a conversion mode.
  3. With Live mode on, the result updates automatically as you type.
  4. Turn Live mode off to convert manually with the Convert button.
  5. Click Copy to copy the converted text to your clipboard.

Examples

Full-width katakana → Half-width katakana

ガッツポーズ → ｶﾞｯﾂﾎﾟｰｽﾞ

Half-width katakana → Full-width katakana

ｶﾞｯﾂﾎﾟｰｽﾞ → ガッツポーズ

Full-width ASCII → Half-width ASCII

ＡＢ１２ → AB12

Half-width ASCII → Full-width ASCII

AB12 → ＡＢ１２

Full-width space → Half-width space

Ａ　Ｂ → Ａ Ｂ

Half-width space → Full-width space

A B → A　B

NFKC normalization

① Ⅳ ㍿ → 1 IV 株式会社

What are full-width and half-width characters?

Full-width characters occupy a square cell (1:1 ratio), like kanji or full-width Latin letters. Half-width characters are narrower (1:0.5 ratio), like standard ASCII letters and digits.

Japanese websites often require a specific width format for names, addresses, phone numbers, and product fields — mixing the two can trigger validation errors.

What is NFKC normalization?

NFKC normalization maps compatibility characters — such as circled numbers (①), Roman numerals (Ⅳ), and full-width letters (Ａ, １) — to their standard Unicode equivalents (1, IV, A).

It is useful for cleaning up text before search indexing or data analysis, where inconsistent character forms can cause mismatches.

Related tools

How to Fix Full-width and Half-width Errors on Japanese Websites

When signing up for a Japanese website, shopping on Amazon Japan or Mercari, or booking a hotel, you may run into error messages like "Please enter in full-width characters (全角で入力してください)" or "Please enter in half-width characters (半角で入力してください)". These errors are usually caused by input forms that distinguish between full-width and half-width character widths. Use the guide below to identify the cause and convert your text to the required format.

📌 Common full-width / half-width requirements by field type

Field Typical requirement Correct example
Name furigana (katakana) Full-width katakana is usually required ヤマダ
Postal code / Phone number Half-width digits are usually required; check whether hyphens are allowed 1234567 / 01012345678
Street number / Apartment number Varies by site; try switching if you get an error 1-2-3 or １－２－３
Email address / Password Half-width letters, digits, and symbols are usually required moji@hako.com

1. Why full-width errors occur on Japanese shopping sites

Characters that look nearly identical — the Latin letter A vs. Ａ, the digit 1 vs. １, or the katakana ｶ vs. カ — are treated as completely different codes by the underlying system. Full-width and half-width characters can easily get mixed in when you paste an address from another app, copy text from a website, or rely on smartphone autocomplete.

2. Furigana input: full-width vs. half-width katakana

Furigana (phonetic reading) fields on Japanese websites typically require full-width katakana. If you entered your name in katakana but keep getting an error, the problem may be that half-width katakana was used instead. Use the [Half-width katakana → Full-width katakana] option on this page to fix it.

*Note: Some older reservation or shipping systems specifically require half-width katakana (半角カナ). Always check the exact wording of the error message.

3. Full-width digits vs. half-width digits

Full-width digits like １２３４ take up a square cell each, while half-width digits 1234 use standard ASCII width. Payment card numbers, postal codes, and phone number fields often reject full-width digits. Use [Full-width ASCII → Half-width ASCII] to normalize them.

4. The invisible full-width space problem

One of the trickiest error sources is the space character. When a Japanese IME is active, pressing the spacebar can insert a full-width space (　) instead of a regular half-width space. A full-width space hidden between a first and last name, inside an address, or before a building name can cause a form to reject the input entirely. If you cannot find the cause of an error, try running [Full-width space → Half-width space].

5. Bulk text cleanup with NFKC normalization

When collecting Japanese product names at scale for data analysis, or preparing listings for an online store, NFKC normalization is a handy one-step cleanup. It converts compatibility characters like ①, Ⅳ, and ㍿ alongside full-width alphanumerics into standard text (1, IV, 株式会社), making search and comparison far more reliable.

🛑 Checklist when you hit an error on a Japanese site

  • Are phone numbers, postal codes, and card numbers in half-width digits? (e.g. 1234)
  • Is the furigana field filled with full-width katakana? (e.g. ヤマダ)
  • Is there an invisible full-width space hiding somewhere in the text?
  • Do any compatibility characters (①, Ⅰ, etc.) appear in addresses or product names?