The free online Excel converter changes a spreadsheet between XLSX, CSV, TSV, JSON and ODS, reading an XLS or an ODS as input too. Because it runs in the browser with SheetJS, the data is never uploaded.
Spreadsheet format work by OnlinePCApps since 2013
A spreadsheet in the wrong format will not import, will not load into an app or will not read in another program. The free online Excel converter puts the data in the format the job needs.
Databases, ETL pipelines and most import screens expect CSV, not XLSX. Converting a workbook to CSV strips the Excel layer and leaves plain rows that load into Postgres, MySQL, a CRM or an analytics tool without a hitch.
An app, an API or a test needs structured data, not a workbook. Converting to JSON maps the header row to keys and each row to a record, ready to drop into a request, a seed script or a JavaScript file.
A payroll sheet, a client list or a budget should not sit on an outside server for a format change. SheetJS runs in the browser, so the workbook stays on the device while it converts.
Drag the workbook onto the panel above, or browse to it on the device. An XLSX, XLS, XLSB, XLSM, ODS or CSV all work. The format is recognised on its own.
Choose the output, such as CSV, JSON, TSV, XLSX, ODS or an HTML table. When a workbook holds more than one sheet, a picker sets which tab to convert, since a CSV holds a single sheet.
Save the converted file, or grab a whole batch as a ZIP. The original workbook stays untouched, so the same data can be converted again to another format at any time.
To convert a spreadsheet is to rewrite the same data in a different format. The tool does that on the device with SheetJS.
The same data is rewritten from one format into another, from XLSX to CSV, CSV to XLSX, XLSX to JSON and the rest. The input format is detected on its own, so only the output has to be chosen.
A workbook with several tabs shows a sheet picker, since a CSV or a TSV holds one sheet. The chosen tab is written out, and each other tab can be converted in turn to its own file.
Converting to JSON maps the first row to keys, so each row becomes a record ready for an API or a script. An array of arrays is written instead where raw rows are wanted, with numbers and dates typed.
Excel date serials are written as ISO 8601, so a date reads as 2026-01-31 rather than a raw number. A CSV follows the RFC 4180 rules, wrapping any field that holds a comma or a line break in quotes.
To convert a spreadsheet, to change an XLSX to CSV and to turn Excel into JSON all name the same task. A search for Excel converter or spreadsheet converter reaches this tool, and the original workbook is left as it is.
A conversion rewrites the data into a new format. These points decide how the result lands.
| The case | Result | What happens and why |
|---|---|---|
| XLSX and CSV | clean | Excel workbooks and CSV convert between one another, the core of the tool. |
| XLS, XLSB, XLSM | read as input | Older, binary and macro-enabled Excel files are read, XLSB being one that few tools besides Excel open. |
| Password protected | unlock first | A workbook locked with a password is opened and saved without it before converting. |
| ODS | OpenDocument | A genuine LibreOffice ODS is read and written, not a renamed CSV. |
| JSON | header keys | The first row maps to keys, or an array of arrays is written for raw rows. |
| Multiple sheets | one per file | A CSV or TSV holds one sheet, so a picker sets which tab is written. |
| Formulas | values to CSV | A CSV or JSON keeps the computed values, while XLSX and ODS can carry formulas. |
| Formatting | not in CSV | Colours, fonts and charts do not survive a move to CSV, JSON or TSV. |
| Dates | ISO 8601 | Excel date serials are written as a plain date such as 2026-01-31. |
| Where it runs | on the device | The data is rewritten in the browser, so the workbook is not uploaded. |
Workbooks, Sheets and Plain Data
A spreadsheet format decides how much lives in the file beyond the raw numbers. XLSX, the modern Excel format, is a rich container that holds several sheets, formulas, colours, fonts and charts. CSV is the opposite, plain text with one value per cell, one row per line and nothing else. This gap sets the honest rules of a conversion. Moving XLSX to CSV keeps the values of a single sheet and drops the formulas, the formatting and the extra tabs, which is exactly why CSV loads into a database or a pipeline that an XLSX would choke. Moving the other way, CSV to XLSX or to ODS, wraps the same rows in a workbook that Excel and LibreOffice open natively. Formulas survive a move to another spreadsheet format such as XLSX or ODS, while a CSV or a JSON keeps the computed value alone. Dates come across as ISO 8601, and a CSV follows the RFC 4180 rules for quoting. The whole conversion is handled by SheetJS, which can run in a Web Worker so a large workbook does not freeze the page. The references below define the formats.
Both change a spreadsheet's format. The trade is real, and business data is often sensitive.
| Point of comparison | This tool Converted in the browser On the device | Hosted converter Uploaded and converted on a server |
|---|---|---|
| Where the data goes | Stays on the device | Uploaded to a server |
| Price and caps | Free with no file cap | Free tier often capped |
| Millions of rows | Held in tab memory | Reads straight from disk |
| Keep formulas and charts | Data and formulas to a sheet | Excel keeps charts and macros |
| Hundreds of files | A file at a time in the browser | Batch on their hardware |
Those last three rows favour a desktop program, since millions of rows, live formulas and charts or a run of many files each call for more than a browser tab holds. For an everyday workbook the first two rows are what count. The data stays on the machine, and the conversion is free with no cap.
The workbook is read and rewritten inside the browser by SheetJS, so the work is client-side and the data stays on the machine that opened it. No copy is passed to a server for the job.
A spreadsheet can be a private thing, a payroll run, a client list or a budget never meant to sit on an outside server. A hosted converter has to upload the whole file to change its format, far more exposure than a format swap is worth.
Each of these changes a spreadsheet's format. They differ in effort, in cost and in where the file goes.
Excel, LibreOffice and the command line all convert well, yet each needs an install or a terminal. Google Sheets uploads the data. This page stays local like the desktop apps while adding JSON output and a sheet picker with nothing to set up.
A little context sets what to expect.
CSV suits a database or an import screen. JSON suits an app or an API. XLSX or ODS suits a person who will open and edit the sheet, and the destination usually points to one.
Moving to CSV keeps the values of one sheet and drops formulas, colours, charts and the other tabs. To hold onto those, convert to XLSX or ODS rather than CSV or JSON.
A workbook with several tabs writes one sheet to a CSV or a TSV. The picker sets which tab to convert, so pick the sheet that holds the data the destination needs before downloading.
The browser handles a workbook in memory, which fits an everyday file. A sheet of millions of rows, or a folder of files to convert together, belongs on the desktop edition, which reads from disk and rewrites the whole set in one pass.
Point it at a folder of workbooks and every file is rewritten to the target format in a single run, saved beside the original.
A sheet with hundreds of thousands or millions of rows is read straight from disk, past the memory a browser tab holds.
Saved presets set the output format, the sheet rule and the date handling in one click, ready for a repeated workflow.
Free and online, with no sign-up and no upload. Change a spreadsheet's format in the browser, all on the device.