How to Open a CSV File

What is a CSV file?

CSV stands for Comma-Separated Values. It's plain text: each line is one row, and within a row, fields are separated by a delimiter — usually a comma, though semicolons and tabs are also extremely common depending on the exporting program's locale settings. There's no formatting, no formulas, no multiple sheets — just the raw data, which is exactly why it's the most universal format for moving tabular data between completely different programs, databases and programming languages.

The closest thing to an official standard is RFC 4180, which defines how fields containing the delimiter, quotes, or line breaks should be wrapped in double quotes. In practice, real-world CSV files vary a lot in how strictly they follow it — which is exactly what trips up naive parsers, and what this page's tool is built to handle correctly.

How to open a CSV file on Windows

1. Double-click it — it opens in Excel by default on most Windows installs.
2. If it looks garbled or crammed into one column, don't fight Excel's import settings — use the tool on this page instead, which detects the real delimiter automatically.
3. To open it as plain text instead, right-click → Open with → Notepad (or any text editor).

How to open a CSV file on Mac & online

1. Mac: Double-click the file — it opens in Numbers by default, or Excel if installed.
2. Google Sheets: File → Import, or just drag the file into sheets.google.com.
3. Any platform: the tool on this page works identically everywhere a modern browser runs, with no spreadsheet software required at all.

The "everything's in one column" problem

This is, by far, the single most common CSV complaint. It happens because "comma-separated" is really more of a convention than a strict rule: many programs — especially ones set to a European locale, where a comma is the decimal separator for numbers — export CSV files using a semicolon instead. Excel then opens the file using whatever delimiter your system's regional settings expect, and if that guess is wrong, every field lands in a single column.

The fix isn't to re-export the file differently — it's to tell your spreadsheet program (or, more reliably, use the tool on this page) what the real delimiter actually is. This page's tool tests the comma, semicolon, tab and pipe against the file's own first several lines and picks whichever one produces a consistent column count, then reports exactly which one it found.

Import a CSV into Excel the right way (Data > From Text/CSV)

Double-clicking a CSV lets Excel guess the delimiter, the text encoding and every column's data type — and those guesses are behind most "my CSV is broken" complaints. Importing it instead gives you a preview where you choose all three before anything lands in the sheet. In Excel for Microsoft 365, Excel 2021 and Excel 2019 on Windows:

1. Open a blank workbook (don't double-click the CSV itself).
2. Go to the Data tab and click From Text/CSV in the Get & Transform Data group, then pick your file and click Import.
3. In the preview window, set File Origin to 65001 : Unicode (UTF-8) if accented letters, € signs or non-Latin text look wrong.
4. Set Delimiter to what the file really uses (Comma, Semicolon, Tab…) — the tool at the top of this page tells you which one it is.
5. Set Data Type Detection to Do not detect data types if you need to keep leading zeros, long ID numbers or codes that look like dates exactly as they are.
6. Click Load. To set individual columns to Text instead, click Transform Data, select the column, and choose Data Type: Text before clicking Close & Load.

Prefer the old step-by-step wizard? In Excel for Windows, go to File > Options > Data and tick From Text (Legacy) under "Show legacy data import wizards". It then appears under Data > Get Data > Legacy Wizards, and its third step lets you mark any column as Text. On Excel for Mac, use File > Import, choose CSV file, and the same kind of wizard (delimiter, encoding, column format) opens.

Excel removed leading zeros, changed numbers to dates, or shows 1.23E+15

The CSV file itself is almost never damaged when this happens — Excel converts the values as it opens the file. Open the CSV in Notepad or in the tool above and you'll see the original values are still there. The three classic conversions:

• Leading zeros dropped: a ZIP code like 02134 or an ID like 000184 is treated as a number and shown as 2134 or 184.
• Long numbers cut to 15 digits: a 16-digit reference such as 4111111111111111 appears as 4.11111E+15, and the stored value becomes 4111111111111110 — Excel keeps only 15 significant digits.
• Codes turned into dates: values like 3-4, MARCH1 or 1/2 become 4-Mar, 1-Mar and 2-Jan (the exact result depends on your regional date format).

How to stop it

• Import instead of double-clicking and choose Do not detect data types, or set those columns to Text (see the import steps above). Formatting the cells as Text after opening does not bring the lost zeros or digits back.
• Microsoft 365 on Windows has switches for this under File > Options > Data > Automatic data conversion: you can turn off removing leading zeros, converting long numbers to scientific notation, converting digits around the letter "E", and converting letter-and-number combinations to dates.
• Don't save the CSV back from Excel after it has converted values — saving writes 2134 and 4-Mar into the file and makes the change permanent. Keep the original and work on a copy.
• If you produce the CSV yourself, there is no reliable in-file trick that works in every program; the robust fix is on the importing side. If a spreadsheet will be the final destination anyway, deliver an .xlsx with Text-formatted columns using the CSV to XLSX converter.

Accents show as "é" or "�": fixing CSV encoding

If José turns into José, the file is UTF-8 but is being read as the older Windows-1252 ("ANSI") encoding. If it turns into Jos� (a diamond with a question mark), it's the reverse: an ANSI/Windows-1252 file being read as UTF-8. The data is fine; only the interpretation is wrong.

• Excel, opening: import with Data > From Text/CSV and set File Origin to 65001 : Unicode (UTF-8) (or 1252 : Western European (Windows) for the reverse case). Excel only recognizes UTF-8 on a plain double-click when the file starts with a byte order mark (BOM); the tool on this page reports whether the file has one.
• Excel, saving: in File > Save As, choose CSV UTF-8 (Comma delimited) (*.csv) rather than CSV (Comma delimited). The plain option writes the local ANSI code page, and characters it can't represent are replaced with question marks.
• Notepad (Windows 11): File > Save as has an Encoding drop-down at the bottom, so you can re-save a file as UTF-8 with BOM, which Excel then opens correctly with a double-click.
• Google Sheets and Numbers assume UTF-8, which is the right choice for nearly all modern exports.

Open a CSV in Google Sheets (and keep your data unchanged)

1. Open a spreadsheet at sheets.google.com, then go to File > Import > Upload and choose the CSV.
2. Under Import location, pick Create new spreadsheet, Insert new sheet(s) or Replace current sheet.
3. Leave Separator type on Detect automatically, or choose Comma, Tab or Custom (type ; or |) if the preview is wrong.
4. Untick Convert text to numbers, dates, and formulas to keep leading zeros, long IDs and date-like codes exactly as written, then click Import data.

Dragging a CSV into Google Drive and choosing Open with > Google Sheets also works, but it always converts values, so use File > Import when the exact text matters. Google Sheets caps a spreadsheet at 10 million cells.

Open a CSV file on iPhone, iPad or Android

iPhone and iPad: tap the CSV in Mail or the Files app and Quick Look shows it as a simple table. For sorting or editing, tap the Share button and open it in Numbers (free from Apple), the Excel app or Google Sheets.

Android: open it with the Google Sheets or Microsoft Excel app; from Gmail, tap the attachment and choose either app. If your phone only offers a text viewer, you'll see the raw comma-separated lines, which is still useful for checking what's inside.

On any phone, the tool at the top of this page also runs in the mobile browser: tap "Click to choose a file", pick the CSV from Downloads or Files, and it shows the table without installing an app.

Opening very large CSV files (over a million rows)

An Excel worksheet holds at most 1,048,576 rows and 16,384 columns. Double-click a bigger CSV and Excel warns that the file wasn't loaded completely and drops everything past the last row. Your options:

• Excel's Data Model: in the From Text/CSV preview, choose Load To… > Only Create Connection and tick Add this data to the Data Model. The rows are stored without the sheet limit and you analyse them with a PivotTable.
• A text editor built for big files (VS Code, Notepad++, or less in a terminal) lets you look at the raw lines quickly.
• Split it: on Mac or Linux, split -l 500000 big.csv part_ makes 500,000-line pieces (only the first piece keeps the header row).
• Code or a database: Python's pandas (pd.read_csv("big.csv")), DuckDB or SQLite read multi-gigabyte CSVs that no spreadsheet can.

The viewer on this page parses the whole file but displays only the first 500 rows to keep the browser responsive; the total row count and the column-consistency check cover every row.

Common CSV file problems and how to fix them

Numbers turn into dates (e.g. "1-2" becomes "Jan-2")

This is Excel's autocorrect "helpfully" reinterpreting a value on import. It happens at the spreadsheet-app level, not in the file itself — the tool on this page shows every value exactly as stored in the raw file, unaltered.

Special characters look like garbage (mojibake)

This means the file's character encoding doesn't match what's opening it — commonly a UTF-8 file opened as if it were a different encoding, or vice versa. Re-save or re-export as UTF-8 if you control the source.

Some rows have more or fewer columns than others

Almost always a text field containing the delimiter character without being wrapped in quotes, per RFC 4180. The tool on this page flags exactly how many rows are affected so you can find and fix them.

Related file extensions

Technical references

CSV's closest thing to a formal specification is an IETF informational RFC, documenting the format most real-world implementations converged on.

• RFC 4180 — Common Format and MIME Type for Comma-Separated Values (CSV) Files — The IETF specification this tool's quoting and escaping rules follow.

Frequently asked questions