CSV vs XLSX: What’s the Difference and When to Use Each
CSV is a plain-text file that stores one table as comma-separated rows; XLSX is Excel’s compressed, multi-sheet format that also stores formatting, formulas, multiple tabs and data types. Use CSV when you need a simple, universal file any program can read; use XLSX when you need sheets, formulas, or formatting preserved. This guide explains the real differences and how to get data out of either.
The one-line difference
- CSV (.csv) — plain text. One table, rows separated by line breaks, values by commas. No formatting, no formulas, no tabs. Opens in anything.
- XLSX (.xlsx) — a zipped bundle of XML files. Multiple sheets, cell formatting, formulas, data types (dates, numbers, currency), charts. Needs a spreadsheet app or a library to read.
Side by side
| CSV | XLSX | |
|---|---|---|
| What it is | Plain text | Zipped XML (Open XML) |
| Sheets | One only | Many |
| Formulas | No (values only) | Yes |
| Formatting / colours | No | Yes |
| Data types | Everything is text | Dates, numbers, currency preserved |
| File size | Smaller | Larger, but compressed |
| Opens in | Any text editor, any tool | Excel, Sheets, Numbers, libraries |
| Best for | Imports, exports, data exchange | Working documents with structure |
When to use which
Choose CSV when you’re moving data between systems — importing into a database, feeding a script, or handing a clean table to another tool. Its simplicity is the point: no app can disagree about what a CSV means.
Choose XLSX when a human will work in the file — you need more than one sheet, want formulas to keep calculating, or need dates and currency to stay formatted. CSV would flatten all of that away.
The gotchas that catch people out
- CSV keeps only the active sheet. Saving a multi-tab workbook as CSV silently drops every tab but the current one. Export each sheet separately.
- CSV stores formula results, not formulas. When you save XLSX→CSV,
=A1+B1becomes the number it evaluated to. Usually what you want when extracting data — but know it’s one-way. - Leading zeros and long numbers. A ZIP code like
02139or a 16-digit card number can lose its leading zero or get mangled into scientific notation when a CSV is opened in Excel. XLSX preserves the intended type. - Delimiters and encodings. “CSV” isn’t always commas — European locales use semicolons — and non-UTF-8 encodings break accented characters. XLSX sidesteps both.
How to get the data out of either
To pull specific columns or sheets out of a native Excel file without opening Excel, use the extract data from Excel XLSX tool — it reads the workbook in your browser, lets you pick the sheet and columns, and never uploads the file. For a plain CSV, the CSV column extractor does the same column-picking job. Both run entirely on your device, which matters because spreadsheets are often the most sensitive files you own.
Frequently asked questions
Is XLSX better than CSV?
Neither is “better” — they solve different problems. CSV wins for simple, universal data exchange; XLSX wins when you need sheets, formulas, formatting or data types preserved.
Does converting XLSX to CSV lose data?
It can. CSV keeps only the active sheet and stores formula results rather than the formulas, and drops all formatting. The cell values survive; the structure around them does not.
How do I extract data from an XLSX file without Excel?
Open it in a browser-based extract data from Excel XLSX tool, pick the sheet and columns you need, and export — no Excel and no upload required.
Why does my CSV mangle ZIP codes or long numbers?
Because CSV has no data types — everything is text, and the spreadsheet app guesses when it opens the file, often stripping leading zeros or switching to scientific notation. XLSX stores the intended type, so it doesn’t guess.
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Last updated: 16 August 2026.