CSV garbled characters prevention tool
(BOM addition/line feed code conversion)
Solve the problem of garbled CSV characters and broken line breaks in Excel with one click.
UTF-8 Executes BOM addition/deletion, line feed code conversion (LF/CRLF), and end-of-line blank deletion.
or
CSV / TSV / TXT — processed in browser
CSV files saved in Excel may use Shift_JIS (CP932).
If a source file exists, the base name is inherited automatically.
* Content is processed in your browser and never sent to a server.
If both 'Add BOM' and 'Remove BOM' are on, BOM is first removed then added (resulting in exactly one BOM at the start).
✅ Conversion Result
* This is a simplified preview. For strict CSV parsing (quoted newlines, etc.), use a dedicated tool. This tool focuses on BOM and newline conversion for Excel compatibility.
About
When opening a CSV file in Excel, Japanese characters are garbled and line breaks are broken - this is a tool that solves such problems with one click. You can instantly add/delete UTF-8 BOM (Byte Order Mark) and convert line feed codes (LF/CRLF) on your browser.
Also supports loading CSV files saved in Shift_JIS (CP932). Automatically detects the input character code and processes it using the optimal method.All processing is completed within your browser, and no data is ever sent to an external server.
How to Use
Load CSV file
Drag and drop the file or click the "Select File" button. You can also paste text directly. Please switch the input character code for Shift_JIS files.
Set conversion options
Select options according to your purpose, such as "Add UTF-8 BOM" or "Unify new line code to CRLF". If "Automatic Update" is ON, the results will be reflected immediately.
Copy or save result
Copy the conversion result to your clipboard or save it as a CSV file. The file name is automatically generated from the original file.
Glossary
- CSV (Comma Separated Values)
- A plain text file format that uses commas to separate values. A standard for data exchange between spreadsheets and databases.
- BOM (Byte Order Mark)
- An invisible marker at the beginning of a text file indicating it is encoded in UTF-8. Without it, Microsoft Excel often scrambles UTF-8 characters.
- Line Endings (CR / LF)
- Invisible characters signifying the end of a line. Windows uses CRLF (Carriage Return + Line Feed) while Unix/Linux/Mac use LF only. Mismatches cause import errors.
- Mojibake (Scrambled Text)
- The phenomenon where characters are displayed incorrectly (as random symbols) because the software is interpreting the file with the wrong character encoding.
- UTF-8
- The dominant character encoding for the web. While developers prefer UTF-8 "without BOM", business users need UTF-8 "with BOM" so Excel opens it automatically.
- Blob API
- An HTML5 feature used by this tool to manipulate file binary data entirely within the browser memory, preventing the need for server uploads.
- Batch Processing
- The capability to process multiple files simultaneously. You can drag and drop 10 files, and the tool outputs them zipped with consistent encoding.
FAQ
- Q.Are my CSV files sent to your servers?
- No, they never leave your device. All reading, BOM addition/deletion, and newline processing is done securely within your local web browser. You can safely process highly confidential business data.
- Q.Why do foreign characters look weird when I open a CSV in Excel?
- Excel defaults to local Windows encodings like Shift_JIS unless it detects a UTF-8 BOM. Toggle 'Add UTF-8 BOM' on, convert, and save. When you open the newly saved file in Excel, the characters will display perfectly.
- Q.When loading a Shift_JIS (CP932) CSV, the characters are garbled.
- If automatic detection fails, change the 'Input Encoding' dropdown to 'Shift_JIS (CP932)' and load the file again. This tool outputs UTF-8, but you can manually specify the input encoding.
- Q.Why did my system import fail with a 'newline error'?
- Many web databases and server systems (like Linux/Mac) expect LF line endings. If the CSV was created on Windows (CRLF), it may cause errors. Change the 'Newline Code' setting to 'Normalize to LF (\n)' and convert again.
- Q.Is there a file size limit for the CSVs?
- Because this tool processes files inside your browser's memory, the maximum supported file size is around 15MB. Extremely large files will cause a loading error or severely slow down your browser.
- Q.Will this overwrite or delete my original files?
- No. The tool reads your file, processes it in memory, and generates a completely new file for you to save. Your original files on your computer are never altered or deleted.
Use Cases
Countermeasures against Excel garbled characters in business CSV
Add a BOM to UTF-8 CSVs exported from core systems before opening them in Excel.
Unified line break code in development environment
Fix mixed CRLF and LF with one click when sharing CSV between Mac and Windows.
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