Converting fullwidth digits can also change kana, spaces and punctuation. The Fullwidth/Halfwidth Converter applies its selected direction to all supported characters. It has no digits-only option. Test a short sample before converting an entire record.
Exact inputs and outputs
| Input | Direction | Output |
|---|---|---|
ＡＢＣ１２３！？ |
To halfwidth | ABC123!? |
ガ パ ヴ |
To halfwidth | ｶﾞ ﾊﾟ ｳﾞ |
ABC123 ｶﾞ |
To fullwidth | ＡＢＣ１２３ ガ |
あいう漢字 |
Either | Unchanged |
ヵヶ |
To halfwidth | ｶｹ |
｡｢｣､ |
To fullwidth | Unchanged in this implementation |
Converting ASCII to fullwidth also changes ordinary spaces and punctuation. Applying it to email addresses, URLs, source code or CSV delimiters can make them unusable. Extract only the fields that need conversion.
Displayed width depends on the font. Fullwidth does not universally mean two bytes: UTF-8 encodes A in one byte and Ａ in three.
Why ガ and ｶﾞ have different counts
| Representation | Code points | Count | UTF-8 bytes |
|---|---|---|---|
ガ |
U+30AC | 1 | 3 |
ｶﾞ |
U+FF76 + U+FF9E | 2 | 6 |
ガ (decomposed) |
U+30AB + U+3099 | 2 | 6 |
The decomposed last row can look identical while remaining a different sequence. This converter handles the supported pairs ガ/ｶﾞ; it does not universally compose decomposed Unicode. Check the character and byte count guide before submitting a length-limited field.
Width conversion is not NFKC normalization
Unicode NFKC also folds compatibility characters. For example, NFKC maps ① to 1, whereas this width converter leaves it unchanged. Neither transformation should be applied indiscriminately to names, scholarly notation or identifiers.
The implementation uses mapping tables and the fullwidth ASCII code offset. It is not a full Unicode NFKC implementation. Nor is every round trip reversible: ヵ → ｶ → カ loses the small-kana distinction. Retain the original separately from any normalized comparison key.
Form and CSV workflow
- Check whether the destination requires ASCII digits, ASCII letters or halfwidth kana; these are different requirements.
- Keep the original and paste only the field needing conversion.
- Select the direction and compare with the examples above.
- Copy the output and check length, voicing marks, spaces and leading zeros at the destination.
The input stays unchanged. Every button reads the input field, so to transform the output again you must paste it back into the input. Processing occurs in the browser; the implementation does not upload the text.
Frequently asked questions
Can I convert only digits?
There is no digits-only switch. Extract that field, or inspect all other characters in the result.
Should all personal names be standardized?
Follow the receiving system’s requirements and preserve the person’s original spelling. Conversion does not guarantee identity matching across systems.
Should I convert a password?
Do not silently change an existing password: width variants are different characters and may not match the registered value.
Return to the same workflow
Open the width converter and reproduce the examples above. Use the favorite control near the tool name to reopen it from My Tools in the same browser. Favorites store tool choices, not the entered content. Clearing site data removes them.
Scope of this update
On October 24, 2026, we compared these examples with the published implementation. Primary references explain the underlying rules; the tables describe this tool. This is not a speed or capacity benchmark.
