Excel to CSV Converter

About Excel to CSV Converter

Drop an .xlsx or .xls workbook and the first worksheet comes back as a comma-separated text file. Formulas are exported as their calculated values, fields containing commas or line breaks are quoted properly, and the file is written as UTF-8 with a byte-order mark so Excel reopens it without mangling accented characters. The workbook is parsed in this browser tab and never uploaded.

Why anything still wants CSV

XLSX is a zipped bundle of XML describing sheets, styles, formulas and relationships — rich, and awkward for anything that is not a spreadsheet application. CSV is one table in plain text, which is why it remains the lingua franca for bulk imports: database loaders, CRM and mailing-list importers, analytics pipelines, and command-line tools all take CSV and most take nothing else. Converting is about reducing a document to the data inside it so another system can read it without understanding Excel.

Exactly what survives the conversion

Kept: every cell value in the first sheet, in its original row and column position; the results of formulas, taken from the values stored in the workbook; text exactly as displayed, including dates and currency in whatever format the cell was using; and blank rows, which are emitted as empty lines so row alignment matches the original.

Lost, necessarily: every other sheet, since a CSV holds one table; all formatting — fonts, fills, borders, number formats as formats rather than as text, conditional rules, column widths; charts, images, pivot tables, comments, data validation and macros; and the formulas themselves, which become their answers. Merged cells deserve a specific warning: the value appears in the first cell of the merge and the remainder come out empty, which is a common way for a title row to end up misaligned against the data beneath it.

The first-sheet rule, and how to work with it

Only the sheet in the first tab position is converted, regardless of which one was active when the workbook was saved, and there is no picker. For a multi-sheet workbook you therefore either reorder the tabs before converting, or run the conversion once per sheet, moving each to the front in turn. It is a real limitation rather than an oversight — CSV genuinely cannot express more than one table — but it does mean a monthly report split across twelve tabs takes twelve passes.

Two encoding details that save an afternoon

The output begins with a byte-order mark. That single invisible marker is what makes Excel open the file as UTF-8 instead of guessing your system code page and turning every accented surname into nonsense. Nearly every consumer ignores it harmlessly, but a strict parser may hand you a first column name with an extra character glued to the front — if you see that, drop the first three bytes. Second, dates export as the text the cell was displaying, so a workbook formatted day-first produces day-first text that a month-first importer will happily misread. Reformatting date columns to ISO order before converting removes the ambiguity for good.

Scale and privacy

The whole workbook is loaded into memory, parsed and rendered to a string on the page's main thread, so files in the low tens of megabytes are comfortable and considerably larger ones will make the tab unresponsive. Macro-enabled and binary workbook formats are not accepted by the picker; save a copy as .xlsx first. Everything runs locally with no request at any point — which matters, because the spreadsheets people most often need converted are exactly the payroll, pricing and customer files that should never be uploaded to a stranger's server. To go the other way, use the CSV to Excel converter.