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When a CSV opens as garbled text in Excel or Notepad, this tool reads it back correctly and re-saves it in the encoding you need. Open a CSV and it first auto-detects the character encoding (UTF-8 or Shift_JIS), decodes it correctly, and shows a table preview so you can confirm it's readable. Then pick a "Save as" encoding and download. The most common reason a CSV is garbled in Excel is that the file is UTF-8 without a BOM but Excel assumes Shift_JIS, so the default is "UTF-8 with BOM (Excel)": the BOM (a marker at the start) tells Excel the file is UTF-8 so non-ASCII text displays correctly. If an older in-house system only accepts Shift_JIS (ANSI), you can save as that instead. If auto-detection guesses wrong, switch the "Source encoding" to UTF-8 or Shift_JIS manually. Under the hood, reading the file, detecting the encoding, converting, and writing all happen inside your browser in JavaScript — and Shift_JIS output is produced by building a reverse lookup table from the browser's own decoder at runtime, so no extra software or libraries are needed. Your file is never uploaded, stored, or sent to a server, which makes it safe for customer lists, sales figures, or internal spreadsheets you'd rather not put on a cloud converter (and it suits workplaces where uploading files externally is against policy). Note: when saving as Shift_JIS, characters that don't exist in Shift_JIS (some enclosed numbers, special symbols, emoji) are replaced with "?", and the number replaced is shown on screen. Want to turn an .xlsx into CSV first? Try excel-csv, or csv-viewer to inspect a CSV as a table.
How to use
- Click "Open CSV" to pick a file, or drag and drop one onto the page (no app needed). It auto-detects the encoding and shows the correctly decoded contents as a table preview.
- Choose a "Save as" encoding: "UTF-8 with BOM" (default) to fix garbled text in Excel, or "Shift_JIS (ANSI)" for older software. If the preview looks garbled, switch "Source encoding" manually.
- Use "Download CSV" to save it. Your file is never uploaded anywhere.
FAQ
My CSV shows garbled characters in Excel. How do I fix it?
Open the CSV here and save it again with "Save as" set to "UTF-8 with BOM (Excel)" (the default). Most garbling happens because the file is UTF-8 without a BOM while Excel assumes Shift_JIS; the BOM (a marker at the start) tells Excel the file is UTF-8 so text displays correctly. If that doesn't help, the original may be Shift_JIS — switch "Source encoding" to Shift_JIS.
Is the CSV file I open uploaded to a server?
No. The CSV is read into your browser only; detecting the encoding, converting, and writing all run on your device in JavaScript. Nothing is uploaded, stored, or transmitted, so it's safe for customer lists, sales data, or workplaces that forbid uploading files externally.
Can I convert a Shift_JIS (ANSI) CSV to UTF-8, or the other way around?
Yes. It auto-detects UTF-8 vs Shift_JIS when reading (you can override it), then you choose UTF-8 (with or without BOM) or Shift_JIS as the output. It works in both directions — for older systems that only accept Shift_JIS, or newer tools that expect UTF-8.
Can auto-detection guess the encoding wrong?
On short files or CSVs with only a few non-ASCII characters, UTF-8 vs Shift_JIS detection can occasionally be wrong. If the preview looks garbled, switch "Source encoding" to UTF-8 or Shift_JIS manually and the preview will correct itself.
Are any characters lost when saving as Shift_JIS?
Shift_JIS covers fewer characters than UTF-8, so characters that don't exist in it (some enclosed numbers, special symbols, emoji) are replaced with "?" when saving. The tool shows how many were replaced; if losing them is a problem, save as UTF-8 with BOM instead.