CSV identifier import check
Spot leading zeros and long digit strings before importing a file into a spreadsheet.
Why check before import?
Fictional product code 00123 can become 123 when a spreadsheet treats it as a number. A long identifier such as 1234567890123456 can lose precision.
Download a fictional practice CSV (103 bytes). Try it before choosing a private export:
- Choose the downloaded file below and select Read file.
- Select
Code, then Check selected columns. - Expect 3 records checked and 2 flagged cells. Record 1, ending line 2, column 1 has leading zeros. Record 2, ending line 3, column 1 has a long digit string.
Record 3 is a decimal, which this narrow check does not test. All practice values are made up, not account details.
Choose columns that name things, such as product codes, not amounts to calculate. A warning means review your import settings; it does not mean the value is wrong.
1. Read a saved CSV
A UTF-8 comma-separated file, up to 1 MiB (1,048,576 bytes) and 1,000 data rows. The first row must name the columns. More about supported files
2. Choose identifier columns
Only choose columns whose values are identifiers. Names are matched exactly, not trimmed or changed. The file's header names appear here; keep them private.
Your result
No cell values are shown in this report. Positions and counts can still reveal information.
| Record | Ending line | Column | Reason to review |
|---|
Record numbers exclude the header; a quoted field may span several physical lines. This result is not proof of safe import, valid data or unchanged spreadsheet values.
Keep the original export
Choose identifier columns as text in your spreadsheet's import settings. Inspect the preview and compare the imported identifiers with the original file. Formatting a damaged number afterwards cannot recover lost zeros or digits.
Microsoft's guidance on keeping leading zeros and large numbers
Supported files and warning patterns
This reader accepts UTF-8 text, with an optional initial encoding marker (BOM). Limits: 1 MiB (1,048,576 bytes), 1,000 data records and 65,536 UTF-16 text units per field. Some characters use two units. The first record must name the columns.
In chosen columns, only non-empty strings made entirely of digits 0-9 are checked. More than one digit starting with 0 gets a leading-zero warning. More than 15 digits gets a potential precision-loss warning. A value may get both. Spaces, signs, decimals, exponent forms, other digit characters and empty cells are not checked. No warning does not mean these other formats will be preserved.
Use comma separators and double quotes around fields containing commas or line breaks. A quote inside a quoted field is written twice. This strict reader stops on quotes inside unquoted fields, text after a closing quote, unfinished quotes or inconsistent field counts. It accepts LF, CRLF and CR line endings and preserves spaces. It does not recognise every CSV dialect. A semicolon-separated file may appear as one column, so check the displayed column names before continuing.
What stays on your device
The file is read locally, not uploaded, repaired or saved. The whole file and its parsed values stay in this page's background worker until you clear, replace the file, reload or close the page. Clear terminates that worker. Cancel discards the current read or check; jobs stop after 30 seconds. This does not lock the file or create a frozen copy.
This tool does not open or configure your spreadsheet, validate account numbers or recover lost data. Positions and counts can still reveal information. Hosted-page visit counting is explained below; file data is not sent with that count.
Prefer Python? Use the identifier-check guide. Its CSV reader has different grammar and character-count details; unusual CSV forms may give different results.