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Spreadsheet file formats and open datasets

Pick XLSX to keep formulas and formatting, ODS if you work in LibreOffice, and CSV when a program will read the data. The table compares what each format keeps and how large the same workbook becomes. Below it: public datasets with their sources, plus guides and answers on opening, converting and citing them.

How do the five formats compare?

FormatWhat it keepsMedian size vs XLSXOpens in
XLSXFormulas, formatting, all tabs1.0× (median 15.6 KB)Excel, Google Sheets, LibreOffice Calc, Numbers
ODSFormulas, formatting, all tabs0.77×LibreOffice Calc natively; Excel and Google Sheets open it
CSVValues only; one file per tab, zipped0.26×Any text editor, database or script
XML (Excel 2003)Formulas and formatting, all tabs; no tab colours5.7×Excel and older tools; one plain-text file
NumbersValues only, all tabs6.7×Numbers on Mac, iPad and iPhone

Sizes: median over 54 workbooks, written by Sheet Reserve’s own browser writers and measured 9 Oct 2026. How the benchmark was run.

Which public datasets are on the shelf?

DatasetWater

Freshwater withdrawals by country

Freshwater withdrawals by sector, renewable resources and water stress for 186 countries, from the World Bank and FAO AQUASTAT.

4 tabs · 888 formulas

DatasetEconomy

GDP by country, 1990-2025

GDP, GDP per capita and growth for 217 countries and territories, 1990-2025, from the World Bank.

6 tabs · 434 formulas

Every dataset keeps its original units and names its source and licence. See Data sources and licences.

Which free tools convert spreadsheet files in the browser?

Five converters that read your file on your own device and write the result there, with nothing uploaded.

  • CSV to XLSX

    CSV in · XLSX outTurn a CSV, TSV or semicolon-separated file into an Excel .xlsx workbook in your browser. Numbers stay numbers, leading zeros stay text, nothing is uploaded.

  • XLSX to CSV

    XLSX in · CSV or ZIP outConvert an Excel .xlsx workbook to CSV in your browser. Each sheet becomes its own CSV, formulas are written as their last result, and nothing is uploaded.

  • CSV to JSON

    CSV in · JSON outConvert CSV to JSON in your browser: an array of objects or of arrays, numbers typed, no sign-up and no upload. Copy the preview or download the .json file.

  • Delimiter converter

    CSV in · CSV outChange a CSV delimiter between comma, semicolon, tab and pipe, and fix the file Excel opens in one column. Runs in your browser; nothing is uploaded.

  • Leading zeros

    CSV in · XLSX outStop Excel dropping the zeros in ZIP codes, account numbers and IDs. Convert a CSV to .xlsx with the columns you choose written as text. Free, in your browser.

All free spreadsheet tools

Which guides explain formats, formulas and data?

What do people ask about spreadsheet files and data?

Formats

Spreadsheet skills

Open data