A form says “please enter in half-width”, but I can’t tell what’s full-width.

Paste it into the input field and open the “Check for mixing” tab. It searches for full-width letters, digits, and symbols, full-width spaces, half-width katakana, zero-width spaces, and trailing whitespace, and lists the line and column of each. In the highlighted view, full-width spaces are shown as □, trailing half-width spaces as ␣, and invisible characters as ·. Once you know where they are, you can fix them all at once with “Fix for forms”.

Should I standardize on full-width or half-width?

The general rule is half-width for letters, digits, and symbols, and full-width for Japanese (hiragana, katakana, kanji). In particular, email addresses, URLs, passwords, phone numbers, and amounts are unified in half-width. This tool’s “For forms” preset follows this rule, converting letters, digits, symbols, and spaces to half-width and half-width katakana to full-width. If a form specifies something like “full-width katakana”, follow that.

Can I convert half-width katakana (ｱｲｳ) to full-width?

Yes. It converts voiced and semi-voiced marks too, so “ﾊﾟﾝﾀﾞ” becomes “パンダ” and “ｳﾞｧｲｵﾘﾝ” becomes “ヴァイオリン”. In half-width katakana the voiced mark is a separate character, so note that the character count drops when converting to full-width. Conversely, “All half-width” also converts full-width katakana and punctuation and brackets such as “。”, “、”, and “「」” to half-width.

The hyphen in “090ー1234” won’t convert. What is it?

It’s a long-vowel mark (ー), not a hyphen. Typing “-” with Japanese input on can produce a long-vowel mark, and since they look almost the same, it’s an easy mistake to miss. This tool converts long-vowel marks to half-width hyphens only when both neighbors are digits, so ordinary Japanese like “コーヒー” isn’t broken. Dashes (–, —) and full-width minus signs (−) can also be unified to half-width hyphens with “Normalize look-alike symbols to half-width”.

Can I convert hiragana to katakana?

Yes. Choose the “Furigana (full-width katakana)” preset to convert both hiragana and half-width katakana to full-width katakana. “やまだたろう” becomes “ヤマダタロウ”. This preset leaves letters, digits, symbols, and spaces alone, so it works as is for fields that require separating family and given names with a full-width space.

Does the character count treat full-width as two characters?

“Character count” counts both full-width and half-width as one character, the same as social media posts and many forms. It also shows the “full-width 2, half-width 1” count used for manuscript paper and forms, and UTF-8 bytes for systems limited by bytes, so read whichever matches where you’re submitting. For a more detailed breakdown, use the word counter.

Is the text I enter sent anywhere?

No. Conversion and checking run only inside your browser. Even if you paste a draft of an application form with personal information or text from internal documents, it doesn’t leave your device.

Full-Width / Half-Width Converter & Mixed-Width Checker

A converter for when a Japanese form rejects your input with “please enter in half-width (hankaku)”. It converts letters, numbers, symbols, spaces, and katakana to full-width or half-width by character type, and also fixes half-width katakana voiced marks (ｶﾞ → ガ) and long-vowel marks between digits (090ー1234 → 090-1234) in one go. The check tab highlights the line and column of “invisible mixtures” such as full-width letters and digits, full-width spaces, half-width katakana, and zero-width spaces.

Original text

Characters

Emoji count as 1

Excluding spaces

Also excluding line breaks and full-width spaces

Full-width

Characters counted as width 2

Half-width

Characters counted as width 1

Full 2, half 1

Form / manuscript counting

UTF-8 bytes

For checking length limits

Conversion type

Letters, digits, symbols, and spaces become half-width; katakana becomes full-width.

Result

Enter text in the field above

All conversion happens in your browser, and the text you enter is never sent to a server.

ABOUT

About Full-Width / Half-Width Converter & Mixed-Width Checker

The full-width / half-width converter unifies the letters, numbers, symbols, spaces, and katakana in pasted Japanese text to full-width or half-width by character type. It has four presets, “For forms (letters, numbers, and symbols half-width; katakana full-width)”, “All half-width”, “All full-width”, and “Furigana (full-width katakana)”, and you can also change the direction for each character type. It handles half-width katakana voiced marks (ｶﾞ → ガ), dashes and curly quotes, long-vowel marks between digits (090ー1234 → 090-1234), and invisible characters such as zero-width spaces. The check tab highlights and lists the line and column of characters that cause forms to reject input.

How to use Full-Width / Half-Width Converter & Mixed-Width Checker

1Paste text into the input field (character count, byte count, and the full/half-width breakdown appear right away)
2In the “Check for mixing” tab, see where full-width letters and digits, full-width spaces, half-width katakana, and invisible characters are
3Press “Fix for forms”, or choose a preset in the “Convert” tab
4To set details, open the advanced settings and choose “To half-width / To full-width / Keep” for letters, numbers, symbols, spaces, and katakana
5Turn on options as needed, such as converting hiragana to katakana, collapsing repeated spaces, and removing trailing spaces
6Paste into a form or document with “Copy result”

Great for

Find and fix full-width characters when a Japanese form rejects input with “please enter in half-width”
Restore full-width letters, digits, and symbols mixed into a copied email address or URL to half-width
Change the “ー” (long-vowel mark) in phone numbers or postal codes to half-width hyphens
Convert half-width katakana exported from Excel or old business systems to full-width katakana
Convert hiragana or half-width kana to full-width katakana for a name’s furigana field
Remove full-width spaces, trailing whitespace, and zero-width spaces that slipped in when pasting
Make all letters and digits full-width to meet the requirements of forms or manuscripts

Good to know

All conversion happens in your browser, and the text you enter is never sent to a server.
The long-vowel mark “ー” is converted to a half-width hyphen only when both neighbors are digits. Ordinary Japanese like “コーヒー” isn’t changed.
Half-width katakana voiced and semi-voiced marks are written as two characters (ｶ + ﾞ), so converting to full-width reduces them to one character, “ガ”. In the other direction, one character becomes two.
Hiragana have no half-width form, so hiragana and kanji stay as they are even with “All half-width”.
Character count counts each character as one regardless of width. Emoji are also one character, but they count as two in JavaScript and some input fields (UTF-16), so a note appears only in that case.
The “full-width 2, half-width 1” field is the counting method used for manuscript paper and forms. Half-width katakana count as width 1.
UTF-8 bytes are calculated with half-width letters and digits as 1 byte and most Japanese characters as 3 bytes. Use it to check systems with byte-based length limits.
“Remove invisible characters” deletes zero-width spaces and converts special spaces such as no-break spaces to half-width spaces.

Questions this tool answers

Use Full-Width / Half-Width Converter & Mixed-Width Checker for searches like these:

A form rejects input with “please enter in half-width” but I can’t find what’s full-width
I want to convert full-width letters and digits to half-width all at once
I want to convert half-width katakana to full-width katakana
I want to find where full-width spaces are
I want to change “ー” in a phone number to a half-width hyphen
I want to convert hiragana to full-width katakana for a furigana field
I want to make all letters and digits full-width for a form

FAQ

A form says “please enter in half-width”, but I can’t tell what’s full-width.: Paste it into the input field and open the “Check for mixing” tab. It searches for full-width letters, digits, and symbols, full-width spaces, half-width katakana, zero-width spaces, and trailing whitespace, and lists the line and column of each. In the highlighted view, full-width spaces are shown as □, trailing half-width spaces as ␣, and invisible characters as ·. Once you know where they are, you can fix them all at once with “Fix for forms”.
Should I standardize on full-width or half-width?: The general rule is half-width for letters, digits, and symbols, and full-width for Japanese (hiragana, katakana, kanji). In particular, email addresses, URLs, passwords, phone numbers, and amounts are unified in half-width. This tool’s “For forms” preset follows this rule, converting letters, digits, symbols, and spaces to half-width and half-width katakana to full-width. If a form specifies something like “full-width katakana”, follow that.
Can I convert half-width katakana (ｱｲｳ) to full-width?: Yes. It converts voiced and semi-voiced marks too, so “ﾊﾟﾝﾀﾞ” becomes “パンダ” and “ｳﾞｧｲｵﾘﾝ” becomes “ヴァイオリン”. In half-width katakana the voiced mark is a separate character, so note that the character count drops when converting to full-width. Conversely, “All half-width” also converts full-width katakana and punctuation and brackets such as “。”, “、”, and “「」” to half-width.
The hyphen in “090ー1234” won’t convert. What is it?: It’s a long-vowel mark (ー), not a hyphen. Typing “-” with Japanese input on can produce a long-vowel mark, and since they look almost the same, it’s an easy mistake to miss. This tool converts long-vowel marks to half-width hyphens only when both neighbors are digits, so ordinary Japanese like “コーヒー” isn’t broken. Dashes (–, —) and full-width minus signs (−) can also be unified to half-width hyphens with “Normalize look-alike symbols to half-width”.
Can I convert hiragana to katakana?: Yes. Choose the “Furigana (full-width katakana)” preset to convert both hiragana and half-width katakana to full-width katakana. “やまだたろう” becomes “ヤマダタロウ”. This preset leaves letters, digits, symbols, and spaces alone, so it works as is for fields that require separating family and given names with a full-width space.
Does the character count treat full-width as two characters?: “Character count” counts both full-width and half-width as one character, the same as social media posts and many forms. It also shows the “full-width 2, half-width 1” count used for manuscript paper and forms, and UTF-8 bytes for systems limited by bytes, so read whichever matches where you’re submitting. For a more detailed breakdown, use the word counter.
Is the text I enter sent anywhere?: No. Conversion and checking run only inside your browser. Even if you paste a draft of an application form with personal information or text from internal documents, it doesn’t leave your device.

Special Thanks

SOLO GUILD | サービス作るAIエンジニア

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