What is CSV?

The short answer

CSV (Comma-Separated Values) is a plain text format for tabular data — rows and columns, like a spreadsheet. Each line is a row, and each value within a row is separated by a comma.

name,email,age,isPremium
Ana García,ana@example.com,28,true
Luis Martínez,luis@example.com,34,false
Sara Kim,sara@example.com,25,true

The first row is typically a header row with column names. Every other row is a data record.

Why CSV exists

CSV has been used since the 1970s. Its advantages are simple: it is human-readable, universally supported, and extremely compact. Almost every database, spreadsheet app, and data tool can import and export CSV.

Common CSV use cases:

• Exporting data from a database for analysis in Excel or Google Sheets
• Importing bulk records (users, products, orders) into an application
• Sharing datasets between teams or tools
• Data pipeline input/output files

CSV edge cases and gotchas

CSV looks simple but has several tricky rules:

"García, Ana",ana@example.com

"Line one
Line two",other-value

"He said ""hello""",other-value

Reading and writing CSV in code

In JavaScript / Node.js — never parse CSV manually. Use a library:

// npm install papaparse
import Papa from 'papaparse';

// Parse CSV string
const result = Papa.parse(csvString, { header: true });
console.log(result.data);
// [{ name: 'Ana', email: 'ana@example.com', age: '28' }, ...]

// Generate CSV from array of objects
const csv = Papa.unparse(result.data);

In Python — the standard library has csv built in:

import csv

# Reading
with open('data.csv', newline='') as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(row['name'], row['email'])

# Writing
with open('output.csv', 'w', newline='') as f:
    writer = csv.DictWriter(f, fieldnames=['name', 'email'])
    writer.writeheader()
    writer.writerow({'name': 'Ana', 'email': 'ana@example.com'})

CSV vs JSON