Full-width / Half-width Converter
Paste your text and full-width/half-width characters sort themselves out — alphanumerics, symbols, spaces, and katakana included. Handy for cleaning up address books and CSV data. Your input never leaves your browser.
How to use the Full-width / Half-width Converter
Type or paste the text you want to convert into the text area above. The result updates in real time based on the selected conversion direction and the checked character categories. For example, with "Full-width → Half-width" selected, pasting ＡＢＣ１２３ instantly converts it to ABC123.
- Choose a direction: Use the segment buttons to switch between "Full-width → Half-width" and "Half-width → Full-width".
- Select categories: Use the checkboxes to limit conversion to specific character types — Alphanumerics, Symbols, Spaces, and/or Katakana.
- Enter your text: Type or paste text into the input area and the converted result appears the moment you paste. The "Examples (click to try)" chips above the input field load realistic mixed-text samples instantly.
- Copy the result: Click the "Copy" button to copy the converted text to your clipboard.
Common use cases
- Normalizing inconsistent character widths in address books and contact lists (e.g., converting full-width alphanumerics to half-width)
- Standardizing character types in system input forms
- Converting half-width katakana mixed into data to consistent full-width katakana
- Data cleaning for CSV files and spreadsheets
Frequently Asked Questions
Is my input text sent to a server?
No. All conversion is performed entirely in your browser. Your text is never transmitted to or stored on any server, so it is safe to use with personal information or confidential data.
How does half-width to full-width katakana conversion work?
Half-width katakana (ｱ–ﾝ) is mapped to full-width katakana (ア–ン) using a character lookup table. When a half-width voiced mark (ﾞ) or semi-voiced mark (ﾟ) immediately follows a katakana character, the tool correctly combines them into a single composed character such as ガ or パ.
Which alphanumeric and symbol characters are converted?
The tool converts the full-width equivalents of printable ASCII characters — the range ！ to ～ (Unicode code points U+FF01–U+FF5E) — back to half-width "!" to "~" (ASCII 0x21–0x7E), and vice versa. Spaces are converted between half-width space and full-width space (U+3000).