Free offline utility

Your IDs should
survive Excel.

Convert CSV files into a genuine Excel workbook while keeping leading zeros, long identifiers, date strings and formula-like values as literal text.

Download the free offline appUse it in your browser ↗

No checkout, account or subscription. Your CSV files stay on your device.

Illustrative source → workbook
INPUTTEXT IN XLSX
0012300123
123456789012345678123456789012345678
03/04/202603/04/2026
=SUM(1,1)=SUM(1,1)
Local filesNo uploads or conversion API.
One sheet per CSVCombine up to 20 source files.
Source auditSHA-256 hashes and a JSON report.

Before you convert

What are the limits?

Up to 50,000 rows per file, 200 columns and 500,000 cells per workbook. Each file may be up to 10 MB, with 20 MB combined input. Comma, semicolon, tab and pipe separators; UTF-8, UTF-16 and Windows-1252.

How do I use the offline download?

Save CSV-Shield.html and open it in a desktop browser. Select the original CSV files, review the delimiter and preview, then export. The downloaded app contains its own code and runs without a network connection.

Can it recover IDs Excel already changed?

No. Use the original export. This tool preserves the data you provide; it cannot reconstruct lost digits or infer a date’s meaning.

Why is every source cell text?

CSV has no reliable type schema. This tool preserves values instead of guessing. Review and convert the intended numeric columns in Excel before performing calculations. Formula-like values are stored as text.

What use is allowed?

The free app may be used for your own personal or business files. Files remain on your device. Review the exported workbook before using it in a business process.