What is a CSV file?
CSV — plain-text table
What is it?
CSV strips a table down to its bare essentials: one line per record, values separated by commas. Nothing else. No colours, no formulas, no multiple sheets.
That bareness is its strength: virtually any piece of software, any programming language, any database can read a CSV file. It's the common language of data.
History & origin
The format has been in use since the 1970s, long before it was ever described in an official document — that only happened in 2005, and even then without any binding authority.
This lack of a firm standard explains all the headaches people run into with it: everyone implemented it their own way.
Why it is useful
Universal, tiny, readable as plain text, and processable by a script across millions of rows in seconds.
It can be imported into any spreadsheet program and any database.
Limits & drawbacks
The separator is a nightmare: French spreadsheet software uses a semicolon, because the comma is already used as the decimal separator. An English-style CSV opened in a French copy of Excel ends up crammed into a single column.
Add encoding issues — accented characters turning into gibberish — and values that contain a comma themselves, and you've got three-quarters of the world's data-import problems right there.
Practical tips
After converting, always check three things: the separator, the encoding — aim for UTF-8 — and the quotation marks around any values that contain the separator.
To preserve formulas and formatting, convert to XLSX instead. For hierarchical data, CSV is structurally the wrong tool — use JSON instead.
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