Converting CSV to Excel is easy. Converting it without losing leading zeros, turning product codes into dates, and silently truncating at row 1,048,576 — that takes knowing which door you walk through. Here are the three good options, ranked by effort, and the one habit that prevents almost all the damage.
When you open a CSV by double-clicking, Excel guesses a type for every cell based on its contents. Most guesses are fine. The dangerous ones:
The lesson: never let Excel guess. Every method below hands control back to you.
Our CSV to Excel converter runs entirely client-side: paste or load the CSV, it sniffs the delimiter (comma, semicolon, tab, or pipe), parses quoted fields properly, writes number cells only for genuine numbers, and keeps identifiers as text. You get a preview of the parsed rows and a real .xlsx download with a bold header and your chosen sheet name. Because nothing is uploaded, it's also the right choice for customer lists and financial exports that shouldn't touch a third-party server. There's a JSON tab too — an array of objects becomes a worksheet with keys as headers.
Rename data.csv to data.txt, then in Excel go to Data → From Text/CSV. The import preview lets you pick the delimiter, the file origin (crucial for accented characters — use UTF-8), and — in the Transform Data step — set each column's type before anything loads. Mark ZIP, phone, and ID columns as Text and they arrive intact. This is the zero-new-tools path and the one to teach colleagues, because the rename step is what stops Excel from auto-opening with guesses.
If the same export lands every week, build it once with Data → Get Data → From File. Power Query remembers your delimiter, column types, and cleanup steps, and refreshes on demand. It also streams files larger than the sheet limit, so you can aggregate a 3-million-row CSV down to a summary that fits. The trade-off is learning a new ribbon; the payoff is never doing the same cleanup twice.
Delimiter sniffing, quoted-field parsing, leading zeros preserved, no upload. The .xlsx is built in your browser.
Open the CSV to Excel Converter →Semicolon files usually mean a European export. Both our tool and the import wizard detect or let you select semicolons; watch for quoted fields containing them, which a naive find-and-replace into commas will shred.
Quoted commas are why "Nguyen, Lin" must stay one cell. Proper parsers treat double quotes as toggles and doubled quotes ("") as an escaped literal quote. Text-editor hacks don't respect that, which is the second-most-common way hand-converted files corrupt.
UTF-8 and the BOM: files exported with a UTF-8 BOM show a stray  in the first header cell when opened as plain text. Importing with UTF-8 encoding set (or converting via a tool that strips the BOM) keeps headers clean.
| CSV | XLSX | |
|---|---|---|
| Types | Everything is text | Numbers, dates, text, formulas |
| Size of a sheet | Format has no limit | 1,048,576 rows × 16,384 columns |
| Sheets per file | One | Many |
| Formatting | None | Full: fonts, colors, widths, formats |
| Tool compatibility | Universal | Excel, Sheets, Numbers, LibreOffice |
| File size for same data | Larger | Smaller (zip-compressed) |
Keep CSV for interchange — anything that feeds another system, script, or database wants flat text. Take the XLSX when a human has to read, filter, and present the result.
A quick sanity checklist before you trust the new workbook: sort by the ID column and check nothing re-sorted as a number (zeros intact), scan the row count against the source file, and confirm dates look like dates instead of five-digit serials. When the next step is feeding that data onward, the CSV to JSON converter gets you an API-shaped payload, the JSON formatter makes the result reviewable, and SQL formatter cleans up the query you'll write against it.
Don't double-click the file. Either use a converter that writes text cells where they matter (our browser tool does, and nothing gets uploaded), or rename the file to .txt and walk Excel's import wizard, marking columns like ZIP codes and IDs as Text. The damage happens when Excel guesses types on open; both routes take the guesswork away.
Excel treats anything numeric-looking as a number, and numbers don't have leading zeros — 00712 becomes 712. Worse, values like 3-4 become dates. Numbers stored as text (with the green triangle warning) keep their zeros, which is the correct state for identifiers. Fix existing damage by formatting the column as Text and re-entering; the zeros are gone once stripped.
Semicolon delimiters come from European locales where the comma is a decimal separator. Use Data > From Text/CSV and pick Semicolon in the delimiter dropdown, or our converter's auto-detect, which counts delimiters in the first line and picks the winner. Both handle quoted fields that contain the delimiter itself.
CSV keeps one plain-text table: no types, no formatting, no formulas, no second sheet. XLSX is a zipped XML package with typed cells, number formats, formulas, and multiple sheets, capped at 1,048,576 rows by 16,384 columns. If you're round-tripping a file through other tools, CSV is the interchange format; if it's for humans, XLSX wins.
The CSV format has no limit, but an Excel worksheet does: 1,048,576 rows. Opening a bigger CSV truncates it silently at the limit — older Excel versions warned, current ones can just cut. For analysis of larger files, use Power Query (which streams) or a tool like Python's pandas, and aggregate down before the data ever lands on a sheet.