Turn ｗｉｄｅ fullwidth characters like ＡＢＣ１２３ into normal halfwidth ones — or the other way around — and straighten the curly "smart quotes" that word processors sneak into your text. Free, in your browser, nothing uploaded.
What are fullwidth characters?
Fullwidth forms are letters and digits that occupy the same width as CJK characters — common in Japanese documents, old spreadsheets and East Asian web forms. To a computer, Ａ and A are entirely different characters, which silently breaks search, sorting, IDs and CSV imports. Normalising them to one form is step one of any data clean-up.
What this tool fixes
Convert letters and digits (ＡＢＣ→ABC), symbols (！？→!?), ideographic spaces, and katakana (ｶﾀｶﾅ↔カタカナ, with proper dakuten handling) — each toggleable, in either direction. The smart-quote option turns " " ' ' back into straight " and ' so code snippets and CSVs stop breaking after a round-trip through Word or Notion.
How to use it
- Paste your text into the upper box. The converted version appears in the lower box straight away, with a note saying how many characters changed. If nothing needed converting you will see "Nothing to convert".
- Pick the direction at the top left. Full → Half is the default; press the other button for Half → Full.
- Use the checkboxes to limit what gets converted. Letters & digits, symbols, spaces and katakana are on by default; the smart-quote option stays off until you switch it on. To fix only the digits, leave letters & digits ticked and untick the rest.
- Every change to the options recalculates the result immediately. When it looks right, press Copy result.
What gets converted
| Letters & digits | Ａ–Ｚ ａ–ｚ ０–９ ↔ A–Z a–z 0–9 |
|---|---|
| Symbols | Fullwidth ！？（）：／～ and the rest of the ASCII punctuation range ↔ ! ? ( ) : / ~ |
| Spaces | Ideographic space (U+3000) ↔ ordinary space |
| Katakana | Halfwidth ｱｲｳｴｵ ｰ ｡｢｣､･ ↔ fullwidth アイウエオ ー 。「」、・. A trailing dakuten ﾞ or handakuten ﾟ is merged into the preceding letter (ｶﾞ → ガ, ﾊﾟ → パ) and split again in the other direction |
| Smart quotes | “ ” „ → " and ‘ ’ ‚ → ' — applied in either direction |
Anything outside those groups is left alone. Hangul, kanji and hiragana have no halfwidth form, so they pass through untouched, as does any group you have unticked. That makes it easy to pull just the fullwidth digits or brackets out of a document without disturbing the rest.
Where it matters
- Spreadsheets and CSV imports — fullwidth digits like １２３ are text, not numbers, so they drop out of sums and sort wrongly. Convert first, then paste.
- Japanese data — addresses, phone numbers and product codes often mix fullwidth digits with halfwidth katakana, which breaks search and matching. Normalise to one form.
- Code and commands — code copied out of a document may carry an ideographic space or curly quotes, both of which are syntax errors. Turn on the space and smart-quote options.
- Deduplicating names and IDs — the same name stored as Ａ and A never matches. Convert to halfwidth before comparing.
- Going the other way — some Japanese forms and documents require fullwidth letters and digits; switch to Half → Full.
How it works
In Unicode the fullwidth letters, digits and symbols (U+FF01–FF5E) sit exactly 0xFEE0 code points above their halfwidth equivalents (U+0021–007E), so conversion is a fixed offset with no information lost. Katakana are not laid out in the same order, so they go through a lookup table, with the dakuten and handakuten marks handled as part of the preceding character. Everything runs in your browser; the text is never uploaded.
Frequently asked questions
I switched to Half → Full and every English word became wide
With the letters & digits option on, every ASCII letter and digit becomes fullwidth. Untick the groups you do not want touched — to convert only halfwidth katakana, leave just that option ticked.
Why did the character count grow after converting katakana to halfwidth?
That is expected. Voiced letters such as ガ and パ have no single halfwidth form and become two characters, ｶﾞ and ﾊﾟ. Converting back merges them into one again.
What does the "characters converted" number count?
Only the characters that actually changed, not the length of the text. Text that is already halfwidth gives 0 and shows "Nothing to convert".
Is anything saved?
No. The input and the result live only in your browser tab and disappear when you reload. There is no upload and no account.
More free tools
Try the word counter or the typing speed test — everything runs in your browser with no upload.