Documents conversion
Convert CSV to XLSX
Updated Jul 2026
CSV is plain text, just rows of data separated by commas. XLSX is Excel's own format, and it can hold cell formatting, formulas, and multiple sheets that plain CSV can't. To convert, open the CSV in a converter and export it as XLSX. Doing that on your own computer means the data never has to be uploaded anywhere.
- Extension
- .csv
- Type
- Documents
- Typically
- Data, spreadsheets
- Extension
- .xlsx
- Type
- Documents
- Typically
- Spreadsheets
Convert CSV to XLSX on your own computer. Nothing uploads.
How to convert CSV to XLSX
- Open Morphjet and drag in the CSV file you want to convert, or a whole folder of them at once.
- Choose XLSX as the output format.
- Convert. The XLSX file is written next to your original, and nothing leaves your machine.
CSV vs XLSX: what actually changes
| CSV | XLSX | |
|---|---|---|
| File size | Smaller, plain text | Larger, stores formatting and structure |
| Opens everywhere | Yes, any text editor or spreadsheet app | Needs Excel or a compatible spreadsheet app |
| Formatting and styling | None, just raw values | Yes, fonts, colors, column widths |
| Multiple sheets in one file | No, one sheet per file | Yes |
| Formulas | No, only the calculated result is stored as text | Yes, live formulas are kept |
| Numbers and dates stay as typed | Not always, leading zeros and dates can get reinterpreted when opened | Yes, cell formatting keeps them intact |
When to convert, and when not to
Convert CSV to XLSX when you want to open the data in Excel or Numbers with proper formatting, add formulas, or combine several tables into one file with multiple sheets.
Keep the CSV if the file just needs to be imported into a database, script, or another tool, since CSV is the simpler, more universal format for moving raw data around.
Why not just use an online converter?
CSV files often hold sensitive rows, customer lists, financial figures, personal records, whatever the spreadsheet was built to track. Uploading that file to an online converter means a stranger's server processes and, however briefly, holds onto that data before sending back an XLSX. Converting on your own computer keeps the entire file, and everything in it, on your machine the whole time.
Questions
Does converting CSV to XLSX change the data?
No. The conversion is lossless, every row and value carries over exactly. What XLSX adds is structure, like column formatting, that CSV never had in the first place.
Will formulas or multiple sheets appear automatically?
No. A CSV only ever holds one flat table of values, so the XLSX starts out the same way. Formulas and extra sheets are things you add afterward inside Excel or another spreadsheet app.
Can I open the XLSX file without Excel?
Yes. Numbers on Mac, Google Sheets, and free spreadsheet apps all open XLSX files. It's just less universal than CSV, which any text editor can read.
Does the XLSX keep leading zeros and dates the way I typed them?
Better than CSV does. CSV stores everything as plain text, so a spreadsheet app has to guess whether '01234' is a number or a code. XLSX can preserve the cell formatting that keeps those values as intended.
Can this be done without uploading the file anywhere?
Yes. Morphjet converts CSV to XLSX right on your computer, so the data never travels over the internet, even with your wifi off.
Morphjet converts CSV, XLSX, and 1,800+ other formats, all on your machine. Launching this July.