What is the difference between CSV and XLSX?

CSV is plain text — rows of comma-separated values with no formatting, formulas, or multiple sheets. XLSX is Excel's native binary format, which keeps data types, formatting, and multiple sheets. Converting CSV to XLSX gives you a real workbook you can style and extend.

Why does my CSV look wrong when I open it directly in Excel?

Excel sometimes misreads the delimiter (comma vs. semicolon in some locales), mangles UTF-8 characters, or turns long numbers into scientific notation. Converting to a proper .xlsx — where columns and encoding are set correctly — avoids those surprises.

What if my data has commas inside fields?

Those fields should be wrapped in double quotes in the CSV (e.g. "Smith, Ann"), which a correct converter respects so the comma stays inside one cell instead of splitting into two columns.

Is my spreadsheet uploaded when I convert it?

No. The CSV is parsed and the .xlsx is built entirely in your browser, so your data never leaves your device.

How to convert CSV to Excel

Opening a CSV straight in Excel often goes wrong — split columns, garbled accents, numbers turned into 1.23E+11. Converting it to a real .xlsx file first fixes all of that. This guide shows how, and how to dodge the common pitfalls.

The fastest way

Drop your file into CSV to Excel and it produces a genuine .xlsx workbook to download. Read on for the edge cases.

CSV vs. XLSX

CSV is just text — no types, no formatting, one sheet. XLSX is Excel's native format, preserving data types, styling, and multiple sheets. Converting gives you a workbook you can actually build on.

Commas, quotes, and encoding

Two things cause most broken imports:

Commas inside fields. A value like Smith, Ann must be quoted — "Smith, Ann" — or it splits into two columns.
Encoding. CSVs should be UTF-8 so accents and symbols survive. A proper conversion sets this correctly rather than leaving Excel to guess.

Check the data first

Before converting, it helps to eyeball the rows and columns. Open the file in the CSV Viewer to confirm it parses the way you expect. And if your source is JSON rather than CSV, turn it into CSV first with JSON to CSV, then convert that to Excel.

A note on privacy

Spreadsheets usually hold real, sometimes sensitive data. CSV to Excel parses and builds the workbook entirely in your browser, so your data is never uploaded.

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