CSV Encoding Converter

What CSV encoding conversion does

This tool converts the character encoding of a CSV file between UTF-8, UTF-8 with BOM, and Shift_JIS / CP932. It does not re-parse or reshape columns — it decodes and re-encodes the text so quoting and layout stay intact.

How to convert CSV encoding

1. Select a CSV file.
2. Confirm or override the input encoding (Auto is available).
3. Choose the output encoding and optional line-ending mode.
4. Convert in your browser and download converted.csv.

UTF-8, UTF-8 BOM, and Shift_JIS

UTF-8 with BOM is the default output for safer Excel / Windows interoperability. Shift_JIS covers common Japanese CP932 / Windows-31J usage. Plain UTF-8 has no BOM.

About Auto detection

Auto checks for a UTF-8 BOM, then tries fatal UTF-8 decode. Only if UTF-8 fails does it fall back to Shift_JIS. Ambiguous cases should be confirmed manually — Auto never claims certainty when it used a fallback.

Local browser processing

CSV encoding conversion is performed in your browser. The file is not uploaded to BizNavi Hub. Leaving or refreshing the page clears in-memory data.

Limits and unsupported characters

One file up to 20 MB. When converting to Shift_JIS, characters that cannot be represented (for example emoji) stop conversion with a clear error — they are never silently replaced with “?”.

Common Excel / mojibake use cases

• Open a Shift_JIS Japanese CSV correctly as UTF-8.
• Add a UTF-8 BOM so Windows Excel displays Japanese correctly.
• Export UTF-8 data as Shift_JIS for a legacy system that requires CP932.

Limitations

XLSX is not supported. Only UTF-8 and Shift_JIS / CP932 are in scope for this MVP. Auto detection can be ambiguous for short ASCII-only files.

FAQ

How do I convert CSV to UTF-8 online?

Choose your CSV, set the input encoding (or Auto), select UTF-8 or UTF-8 BOM as output, then download the result from your browser.

Why does Excel show garbled Japanese?

Excel on Windows often expects UTF-8 with BOM or Shift_JIS. Converting and adding a BOM usually fixes mojibake.

Is my file uploaded?

No. Conversion runs entirely in your browser.

What happens to emoji in Shift_JIS?

Conversion stops with an error listing unsupported code points. Characters are not silently replaced.

Does conversion change CSV quoting?

No. The tool re-encodes text without parsing and rewriting CSV structure.