FREE TOOL · NOTHING UPLOADED
Check a CSV for Excel damage
Drop a CSV that has been through Excel. This page looks for what Excel leaves behind: SEPT2 turned into 2-Sep, a barcode turned into 1.23457E+18, sample 00123 turned into 123. The file is read in this browser tab and never uploaded, so it is safe for unpublished results and patient-adjacent data.
Written by Taha Bayar, a biologist working on laboratory data handover.
One file, or two
With one file the page looks for traces and says what the value probably was. That is a strong hint, not proof: a date in a date column is not damage, and a value Excel changed into another ordinary-looking value leaves no trace.
With the original as well it compares every cell and names the reason for each difference. If the two files are identical byte for byte, it says so; if every value matches but the bytes differ, the file was re-saved (quotes, line endings or encoding changed), and its SHA-256 no longer matches.
What it looks for
| Finding | Example | How it is recognised |
|---|---|---|
| Gene name turned into a date | 1-Mar, Sep-15 | A day and month in the form Excel writes; March, September and December with the numbers the affected genes carry. It suggests the old and the current HGNC name. |
| Text turned into a date | 2-Jan, 01.Ara | Well positions and ratios like 1-2 in English Excel; decimals like 1.12 in Turkish or German Excel. |
| Long number in scientific notation | 1.23457E+18 | Excel's own display for numbers of 12 digits or more. Real measurements such as 1.2E-05 are left alone. |
| Digits lost after the 15th | 1234567890123450000 | Sixteen digits or more, all zeros from the 16th on. |
| Leading zeros removed | 126 among 00123, 00124 | A shorter plain number in a column that is mostly zero-padded. |
| Garbled characters | ü for ü, µ for µ | UTF-8 read as a Western code page. A file that is not UTF-8 at all is reported too. |
What it cannot see
- Precision:
0.80saved as0.8is the same number. Only the comparison shows it. - A value turned into another value that looks normal, such as a date column re-written in a different date format.
- Formats other than CSV and text. An .xlsx has already been through Excel; export it as CSV UTF-8 first.
Why Excel does all this, and how to switch it off, is in Why a CSV changes when Excel opens it. The way to never need this page is to move the instrument's file as bytes and take its SHA-256 at the source; that is what Kionel does for offline instrument PCs.