Check CSV or TSV files, review issues, and export selected changes.
Original source · record numbers include the header.
Your diagnosis will appear here.
Nothing is uploaded, and no values are converted to numbers.Cell values are always treated as text.
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Review the difference before you download.
Select a change on the left to preview it here. Otherwise, every parsed value and record is kept.
Export rewrites CSV syntax: every field is quoted and record endings become CRLF. The file may look different even when all values are unchanged.
Going to Excel? Quotes do not lock a column’s type. Import IDs as Text to protect leading zeros and long numbers. See the quick guide ↗
A SMALL GUIDE TO FEWER SURPRISES
We check quoting, field counts, headers, and UTF-8 decoding. Structural errors block export. To fix them, edit the source in its original app or paste corrected text, then check it again.
A record is a row of fields, even when a quoted field contains several lines. Blank records are kept and flagged separately.
Trimming, empty-record removal, and exact deduplication are optional. All values stay strings. We never guess a date, turn an ID into a number, or fill a missing field.
Formula-like prefixes are flagged. The apostrophe option changes the actual value and is a precaution, not a security guarantee across spreadsheet apps.
In Excel, use Data → From Text/CSV and set ID columns to Text before loading. Excel numeric cells have 15-digit precision. Formatting later cannot restore lost digits or zeros.
A UTF-8 BOM helps Excel recognize Unicode; it does not prevent numeric conversion or formula interpretation.
LOCAL BY DESIGN
This CSV checker processes file contents in your browser. The checker does not upload your files or save their contents in browser storage. Clear data or reload the page to remove its in-memory copy. Downloaded files remain on your device.
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Supported: UTF-8 CSV/TSV with double-quote escaping and a comma, semicolon, tab, or pipe separator. Limits: 5 MiB, 50,000 records including a header, 200 columns, and 1 million cells. No XLSX or legacy-encoding conversion.
The MIT License (MIT) Copyright (c) 2015 Matthew Holt Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.