How to Keep Leading Zeros in a CSV File

An ID like 00123 is text, even though it contains only digits. If a spreadsheet app guesses that the column is numeric, it may display or save 123 instead. This is easy to miss in postal codes, product numbers, and account references.

Check the source before opening it elsewhere

Open the original CSV in Spreadsheet Studio. It reads CSV cells as strings and shows the values before a spreadsheet app applies its own type guesses. Find a row with a known leading-zero code and check that it still reads 00123.

If the original CSV already says 123, the missing zeros cannot be recovered without knowing the intended width. Return to the source system if possible. If the original says 00123, keep a copy of that source file until the next import is checked.

Export without losing the text

You can edit a cell in Spreadsheet Studio and export a fresh CSV or XLSX. An XLSX export stores text values as text cells. A CSV remains plain text, however, so opening that CSV directly in another spreadsheet app may trigger the same automatic number conversion again. Import the column as Text in that app instead of relying on a double-click open.

Microsoft documents how to keep leading zeros and large numbers in Excel, including text-column import options. The exact controls depend on the Excel version.

For code or API work, the CSV to JSON converter produces string values, so a CSV row with 00123 becomes a JSON string rather than the number 123. Check the output before passing it to another system that may coerce types.

Spreadsheet Studio processes the file in your browser. It shows a limited preview on smaller screens, so export and validate a representative set of rows before replacing the original.