What is CSV?

CSV is a text file where each line is a row and commas separate the fields. There is no type system, no formatting and no second sheet. Every value is text until something downstream decides otherwise.

Who uses it

Almost every database, analytics tool and spreadsheet can read and write it, which is why exports default to it.

Reading CSV

Reading CSV means deciding three things the file does not state: which character separates fields, how quotes work, and what encoding the bytes are in. Tablizer sniffs the delimiter from the first few lines, handles quoted fields containing commas and newlines, and reads the file as UTF-8.

Writing CSV

Any value containing the delimiter, a quote or a line break gets wrapped in quotes, and embedded quotes are doubled. That is the rule in RFC 4180 and it is what spreadsheet software expects.

The specification

CSV is defined by RFC 4180. Reading the primary source settles most arguments about edge cases faster than searching for them does.

What it can hold

CSV is a delimited text format. Every value is text; whether the first row is a header is a convention, not part of the format. A machine can read the table back out of it without guessing, which is what makes it safe to convert into and out of.

It keeps

A line break inside a cell, which survives rather than ending the row.
Its own record boundaries. A reader can take one row at a time without loading the file, and a copy that was cut off part way through still yields everything before the cut.

It cannot express

Types. Every value is text. A column of digits is indistinguishable from a column of numbers until something downstream decides to read it as one, which is where a leading zero usually disappears.
A null. An absent value and an empty one look the same, and nothing in the file says which was meant.
Nesting. Cells are flat, so structured values have to be flattened into extra columns or written into one cell as text.
Any formatting. Bold, colour, column widths and merged cells have nowhere to go.

What it looks like

Example CSV

id,name,role,started,hours
007,Halima Yusuf,"Analyst, data",2024-03-15,38.5
012,"Jonah ""Jo"" Pryce",Engineer,2025-11-02,
104,Wei Chen,Manager,2023-06-30,40

Questions

Why does my CSV open with all the data in one column?

The file uses a delimiter your spreadsheet did not expect. Exports from European locales often use semicolons because the comma is the decimal separator there. Change the delimiter in the export options and the columns split correctly.

How do I open CSV files?

Any text editor will show you the contents. To read it as a table, paste it into the converter on this site and it appears in an editable grid. Nothing is uploaded.

Is CSV a good format for sharing data?

It depends who is receiving it. Almost every database, analytics tool and spreadsheet can read and write it, which is why exports default to it. If the recipient is outside that group, a plain CSV travels further than anything else.