CSV ↔ TSV Converter

Convert between comma-separated and tab-separated tables

CSV is a text table whose cells are separated by commas (,); TSV separates them with tab characters. Paste a table into the converter above or open a file, and it detects which character separates the cells and rewrites the table in the format you pick: TSV, comma CSV or semicolon CSV. Cells that are easy to get wrong, such as an address with a comma or a note with a double quote, get their quotes added or removed according to the CSV rules in RFC 4180.

The result appears as a spreadsheet-style grid, and cells that will change when opened in Excel (leading zeros, numbers of 12 digits or more, values that become dates, values that start like a formula) are flagged. You can copy the result or save it as .tsv or .csv, and save as Excel .xlsx to protect those cells. What you paste or open is never sent to a server; it is processed only inside this browser.

When you need to convert between CSV and TSV

Both formats are plain text, so most programs can read them. You convert when the receiving side expects the other format, or when the separator collides with your data.

• Pasting into Excel or Google Sheets: tab-separated text splits into columns on its own when pasted into a sheet. Pasted CSV puts each whole line into a single cell, so converting to TSV before you copy gives you a table at once.
• An import form or tool that insists on one format: product uploads, contact imports and analytics tools often accept only CSV or only TSV. Renaming the file leaves the separators inside unchanged, so every row collapses into one column.
• Data full of commas: addresses, amounts such as 1,250,000 and free-text comments are easier to read as TSV, because no quotes are needed around them.
• CSV files from a European Excel: in regions where the decimal separator is a comma, Excel separates cells with a semicolon (;). Microsoft explains that changing the decimal separator to a comma makes Excel use a semicolon as the list separator. This converter detects semicolon CSV and can also write it.

How to use the converter

1. Add a table: paste into the input box, press Open file, or drop a file onto the box. Clicking the sample selects all of it, so whatever you paste replaces it immediately.
2. Check the read format: next to Auto you will see the detected separator (comma, tab or semicolon). If the columns split wrongly, press the right one yourself.
3. Choose the write format: by default a tab table becomes CSV, and a comma or semicolon table becomes TSV. Press another write button if you need a different format. The ⇄ button in the middle moves the result into the input and swaps the direction.
4. Follow one row: the strip on top shows how a single row changes from input to result, piece by piece, with the separators. Rows that gain or lose quotes come first; use ‹ › or click a row in the grid to see another one.
5. Read the grid and the flagged cells: column letters (A, B, C…) and row numbers match Excel. A cell with a mark in its top-left corner may change in Excel. The chips below step through each kind of cell and explain why.
6. Take the result away: use Copy result to paste it elsewhere, or save a .tsv or .csv file. If you plan to open it in Excel, Excel .xlsx keeps leading zeros and long numbers as they are.

The rules differ by format

The three formats differ not only in the separator but also in what happens when a cell contains that character or a line break. The converter reads and writes with these rules.

RFC 4180 says that fields containing line breaks, double quotes or commas should be enclosed in double quotes, and that a double quote inside a field is written as two double quotes. The TSV type registered with IANA, on the other hand, states that fields that contain tabs are not allowable and defines no quoting. The tab-separated files Excel writes follow the same quoting rules as CSV (this is the excel_tab dialect in the Python csv documentation), so the converter's default TSV follows that way (Excel/Sheets). Choose TSV quotes → Standard only when the receiving program does not understand quotes.

One row in each format

Here is one row with product code 00123, product Apple, Fuji, note "Extra" grade and a fourth cell Orange↵Valencia (a line break inside the cell), written in each format. ↵ stands for a line break inside a cell and ⇥ for a tab.

In semicolon CSV the comma in Apple, Fuji is not a separator, so the cell stays without quotes. In every format 00123 is carried over exactly as written; the leading zeros disappear only when Excel opens the file.

Cells that change when Excel opens the file

CSV and TSV do not change values themselves, but Excel automatically converts text that looks like a number or a date as it opens the file. These are the kinds of cell the converter flags, and why.

There are two ways to protect such cells. First, save with the converter's Excel .xlsx button: only safe numbers are stored as numbers and everything else goes into text-formatted cells, so 00123, order numbers and 12/2 stay as they are. Second, open the CSV through Excel's data import and set that column's format to Text. If you see a cell that starts like a formula in a file from an unknown source, check what it contains before opening it. OWASP warns that such cells can be executed like commands in a spreadsheet.

When accented letters turn into garbage

CSV and TSV have no field that says which character encoding was used, so the program that opens the file has to guess. Microsoft says a UTF-8 CSV saved with a BOM (the three bytes EF BB BF at the very start of the file) opens correctly in Excel. For that reason the converter adds a BOM by default when it saves a CSV file, and not for TSV. A switch in the options row changes this.

When a file is opened, a BOM is followed if present; otherwise the converter tries UTF-8 and, if that fails, reads the file again as Windows-1252, the legacy Western European encoding. Files written by older programs therefore stay readable, and the encoding that was used is shown above the input box. Saving is always UTF-8.

Common mistakes

• Only renaming the extension: renaming data.csv to data.tsv leaves the commas inside as they are. The receiving program finds no tabs and reads each line as one cell.
• Reading semicolon CSV as comma CSV: splitting a European-style line such as 1,5;2,25 at commas cuts the decimals into separate columns. Check that auto-detect picks the semicolon, and choose it yourself if it does not.
• Ignoring rows with a different number of cells: a comma inside an unquoted cell adds one column to that row only. Look for the marked row number in the grid and for the hatched empty slots.
• Putting a notes cell into standard TSV: a cell with a line break cannot be converted to standard TSV. If the receiver is Excel or Google Sheets, keep TSV quotes on Excel/Sheets; if it does not know quotes, fix the line breaks in the source first.
• Opening the result in Excel and saving again: leading zeros, long numbers and values turned into dates are saved in their changed form. If the original values matter, do not edit the result file in Excel; use the .xlsx save instead.

Limits and cautions

• Input is limited to 10 MB and 1,000,000 cells. The grid draws only the first 200 rows and 40 columns, but copy and save include everything.
• Auto-detect looks at the first 30 lines and picks the character that appears most consistently outside quotes. It can be wrong when there is only one column or when the counts differ widely from line to line, so check the result grid.
• The first row is treated as data; headers are not split off. Empty cells, empty rows and spaces around cells are left as they are.
• Formulas, cell formatting and multiple sheets do not exist in CSV or TSV and are not carried over. Excel workbooks (.xlsx) cannot be opened here; save the sheet from Excel as CSV or Text (Tab delimited) first.
• Saving as .xlsx writes one sheet and does not save if Excel's limits (16,384 columns, 32,767 characters per cell) are exceeded.

Reference date The format rules and Excel behavior were checked against the sources on 2026-10-20.

Sources

• 01IETF RFC 4180: Common Format for CSV FilesFields with line breaks, double quotes or commas are enclosed in double quotes; a double quote inside is written twice
• 02IANA: text/tab-separated-valuesFields that contain tabs are not allowable; every record has the same number of fields
• 03Microsoft: Opening CSV UTF-8 files correctly in ExcelA UTF-8 CSV saved with a BOM opens correctly
• 04Microsoft: Keeping leading zeros and large numbersLeading zeros are removed automatically; precision is 15 digits and digits after the 15th become 0
• 05Microsoft: Available number formats in ExcelGeneral shows numbers of 12 or more digits in scientific notation; Text displays what was entered
• 06Microsoft: Stop automatically changing numbers to datesExample: typing 12/2 turns it into 2-Dec
• 07Microsoft: Import or export text (.txt or .csv) filesThe default list separator for CSV is a comma; changing the decimal separator to a comma makes it a semicolon
• 08Microsoft: Excel specifications and limitsWorksheet size 1,048,576 rows by 16,384 columns; 32,767 characters per cell
• 09OWASP: CSV InjectionCells starting with =, +, -, @, a tab or CR may be interpreted as formulas
• 10Python documentation: csv moduleThe excel_tab dialect: the properties of tab-delimited files generated by Excel
• 11WHATWG: Encoding StandardLabels the browser can read, such as windows-1252, and the UTF-8 BOM

Frequently asked questions

Related tools