Spreadsheet Converter
Spreadsheet conversion is about data rather than appearance. What matters is whether cell types survive, how many sheets the target format can hold, and what happens to formulas.
FileTools360 uses SheetJS to parse and write real workbooks, so numbers stay numbers and dates stay dates instead of everything collapsing into text.
Most used spreadsheet converters
Spreadsheet tools
Operations that change a file without changing its format.
All spreadsheet conversions
39 supported conversions. Every one is a working converter, not a placeholder.
Spreadsheet formats explained
Excel Open XML Workbook
.xlsx, .xlsm
The modern Microsoft Excel workbook format.
Best for: Multi-sheet data · Formulas · Business reporting
Legacy Excel Workbook
.xls
Excel's pre-2007 binary workbook.
Best for: Legacy systems that reject XLSX
OpenDocument Spreadsheet
.ods
The open standard spreadsheet format.
Best for: LibreOffice Calc · Open standards policies
Comma-Separated Values
.csv
Flat tabular text — one table, no formatting.
Best for: Data imports and exports · Databases · Scripts
Tab-Separated Values
.tsv, .tab
Like CSV but tab-delimited — safer for text with commas.
Best for: Data pipelines · Text containing commas
Your spreadsheets are not uploaded to a server
Most online converters copy your file onto their own computer, convert it there and send it back — that copy is what “upload” means, and it is the part nobody explains. Nothing here does that. A spreadsheet is rarely about one person. It is usually about hundreds of them, which is what turns an ordinary file into a reportable data breach. Every tool on this page runs inside the browser you are reading this in, so the file is never transmitted, never stored and never seen by anyone. Turn off your Wi-Fi and convert something anyway if you want to watch that be true.
What people actually convert here
Payroll
every colleague's salary, in one file
Customer and member lists
names, emails, phone numbers, addresses
Patient or client records
regulated personal data under HIPAA, GDPR and similar
Financial models and forecasts
numbers a competitor would pay for
Workbooks and flat tables
XLSX, XLS and ODS are workbooks: multiple sheets, formulas, formatting, charts. CSV and TSV are a single flat table of text with none of that.
Converting a workbook to CSV therefore always loses something. Formulas become their computed values, formatting disappears, and only one sheet survives unless you explicitly export them all. FileTools360 warns you when a workbook has more than one sheet rather than silently dropping the rest.
The problems CSV quietly causes
CSV has no type information. A product code like 007 becomes 7, long numbers turn into scientific notation, and dates are interpreted according to whatever locale the reading application assumes.
The separator is not guaranteed either — exports from European systems commonly use semicolons, because the comma is the decimal separator there. FileTools360 detects the delimiter by analysing consistency across rows rather than assuming.
Spreadsheets and JSON
Converting a sheet to JSON turns each row into an object keyed by the header row, which is the shape most APIs and scripts expect.
Going the other way, nested JSON has to be flattened into columns, because a table cannot represent nesting. FileTools360 uses dotted column names so the structure remains readable, and tells you it has done so.
FAQ