XLSX to CSV Converter

Introduction

A spreadsheet workbook can hold many worksheets, formulas, styles, charts, hidden records, macros, and other workbook objects. CSV holds none of that structure. It is plain text arranged as rows and fields, so converting a workbook to CSV means choosing one worksheet and deciding which visible text belongs in the flat result.

That flattening is useful for database imports, analytics pipelines, command-line processing, and systems that do not read Excel workbooks. It is also lossy. Non-selected sheets, formulas as calculations, formatting, merged cells, charts, validation rules, comments, and macros do not become equivalent CSV features.

The delimiter is part of the receiving contract. A comma is common, but some regional and technical imports expect semicolons, tabs, or pipes. A file can still have a .csv name when it uses another separator, so the importer must be configured to use the same delimiter.

Spreadsheet software can interpret text beginning with characters such as =, +, -, or @ as a formula when a CSV is opened. Treat untrusted cell text as active content risk and use a receiving workflow that sanitizes or imports it as text.

A CSV preview can confirm rows and quoting, but it cannot prove the handoff is safe. Open the downloaded file in the actual destination, check column alignment and character encoding, and compare a few source records before replacing or importing data.

How to Use This Tool:

Start with the receiving system's delimiter and formula requirements, then choose the worksheet that contains the handoff data.

1. Browse for one Source workbook in XLSX, XLSM, XLSB, or XLS format. Files larger than 50 MiB are rejected.
2. Choose the Worksheet and Delimiter. Hidden worksheets remain selectable and are labeled so an accidental hidden-sheet export is easier to catch.
3. Set Formula cells to cached values for a data import or to formula text for an audit. Cached values come from the saved workbook and are not recalculated.
4. Use the advanced options to preserve blank rows, trim trailing empty cells, exclude hidden rows and columns, set a date format, or add a UTF-8 byte-order mark to the download.
5. Review the CSV text and conversion warnings, then test the downloaded file with the intended importer before discarding the workbook source.

Interpreting Results:

Row and column counts describe the flattened output, not the full workbook. Compare them with the selected worksheet and check whether blank rows, trailing empty cells, or hidden content changed the shape.

• A formula warning means saved values were used without recalculating the workbook. Open and recalculate the workbook in a trusted spreadsheet application when freshness matters.
• A hidden-data warning means hidden rows or columns remain in the CSV. Exclude them only when that matches the intended handoff.
• A macro warning confirms that macro content was detected but not carried into CSV or executed during conversion.
• For semicolon, tab, or pipe output, configure the importer for that separator even though the downloaded name ends in .csv.

Technical Details:

Workbook decoding produces a bounded snapshot of sheet names, visibility, used ranges, hidden row and column markers, formatted cell values, and formula text. One worksheet is then reduced to a rectangular sequence of strings before CSV quoting is applied.

Transformation Core:

For example, the two fields North, East and He said "go" become "North, East","He said ""go""" with a comma delimiter. The same quoting rule protects embedded line breaks.

Date formatting is applied while workbook cells are decoded. It changes the text placed in CSV, not the workbook's stored date serial. A custom date pattern can therefore improve compatibility, but the receiving parser still decides whether that text becomes a date.

A UTF-8 byte-order mark adds three bytes at the start of the downloaded file. It is omitted from the on-page preview. The mark can help some spreadsheet applications recognize UTF-8, but importers that require text without a BOM should leave it off.

The accepted workbook size is at most 50 MiB, with up to 200 worksheets and 500,000 decoded cells. Empty sheets and outputs that become empty after filtering are rejected.

Limitations and Privacy Notes:

Workbook bytes are read and converted in the current browser tab rather than uploaded to a conversion service. The resulting CSV still contains the selected cell text and should be handled according to the source data's sensitivity.

• Only one worksheet is converted at a time.
• Formatting, charts, images, comments, validation rules, merged-cell behavior, macros, and workbook relationships are not preserved.
• Formulas are never recalculated, and generated CSV cells are not sanitized against spreadsheet formula injection.
• Large or complex workbooks may exceed the file, sheet, or decoded-cell limits.

Worked Examples:

References:

• RFC 4180: Common Format and MIME Type for CSV Files, IETF, October 2005.
• CSV and Text utilities, SheetJS Community Edition documentation.
• Save a workbook to text or CSV format, Microsoft Support.
• Excel formatting and features not transferred to other file formats, Microsoft Support.
• CSV Injection, OWASP Foundation.