// character encoding

What Is UTF-8?

UTF-8 is a character encoding used to represent text inside computers. It provides a way of turning Unicode characters such as letters, numbers, mathematical symbols and characters from many languages into bytes that a computer can store and process.

// definition

UTF-8 turns characters into bytes

UTF-8 stands for Unicode Transformation Format - 8-bit.

It is an encoding system that converts Unicode characters into sequences of bytes.

This allows text to be stored in files, transmitted across networks and interpreted consistently by different computer systems.

// why encoding?

Computers do not store letters directly

When we look at a computer screen, we see characters:

A £ π é 日 😀

But computer storage ultimately consists of binary data. The computer therefore needs a defined system for representing each character using numbers and bytes.

Character → Unicode code point → UTF-8 encoding → Bytes

// unicode

First, understand Unicode

Unicode is a standard that assigns characters unique numerical identifiers called code points.

A Unicode code point is normally written using U+ followed by hexadecimal digits.

Character	Unicode code point
A	U+0041
£	U+00A3
é	U+00E9
π	U+03C0
€	U+20AC
😀	U+1F600

// unicode vs utf-8

Unicode and UTF-8 are not the same thing

This distinction is important.

Unicode

Defines characters and assigns them code points.

UTF-8

Defines how those Unicode code points are encoded into bytes.

Unicode tells us that the pound sign is U+00A3. UTF-8 tells the computer which bytes should be used to represent that character.

// bytes

UTF-8 uses between one and four bytes

UTF-8 is a variable-length encoding.

Different characters require different numbers of bytes.

Character	UTF-8 bytes	Bytes used
A	41	1
£	C2 A3	2
π	CF 80	2
€	E2 82 AC	3
😀	F0 9F 98 80	4

Important: the hexadecimal byte values shown above are the UTF-8 encoding of each character, not the Unicode code point itself.

// ascii compatibility

UTF-8 is compatible with ASCII

One of the reasons UTF-8 became so successful is its compatibility with ASCII.

The first 128 Unicode characters use exactly the same single-byte values as ASCII.

A = U+0041 = UTF-8 byte 41 B = U+0042 = UTF-8 byte 42 1 = U+0031 = UTF-8 byte 31

This means ordinary English text using basic letters, digits and punctuation is very compact in UTF-8.

// multilingual text

UTF-8 can represent text from many languages

UTF-8 is not limited to English.

English: Hello Português: Olá Español: Información Français: Éducation Greek: π Japanese: 日本 Currency: £ € ¥ Mathematics: ≤ ≥ ± √ ∞ Emoji: 😀

All of these characters can exist within the same UTF-8 encoded document.

// encoding errors

What happens when the wrong encoding is used?

Text can become corrupted-looking when software interprets bytes using the wrong character encoding.

For example, a pound sign encoded as UTF-8 may sometimes incorrectly appear as:

Expected: £50 Incorrect interpretation: £50

This type of garbled text is often called mojibake.

The data may not actually be damaged. The same bytes may simply have been interpreted using the wrong encoding.

// txt files

UTF-8 and .txt files

A .txt file tells us that a file contains plain text, but it does not automatically tell us which character encoding was used.

.txt ≠ automatically UTF-8

A text file might use UTF-8, ASCII, Windows-1252 or another encoding.

For modern text files, UTF-8 is generally the most useful and interoperable choice.

// csv files

UTF-8 and CSV

CSV is also a text-based format, so character encoding matters.

Name,City,Amount João,Lisboa,£50 Élodie,Paris,€75 Sofia,Athens,€40

Saving this file using UTF-8 helps preserve accented characters and currency symbols when the file moves between compatible systems.

// xml

UTF-8 and XML

XML documents can explicitly declare their character encoding.

<?xml version="1.0" encoding="UTF-8"?>

This tells the software reading the document that its characters are encoded using UTF-8.

// html

UTF-8 on websites

Websites also need to specify how text should be interpreted.

Modern HTML pages commonly include:

<meta charset="UTF-8">

This tells the browser to interpret the document using UTF-8.

Correct encoding is important for displaying names, symbols, mathematical notation, international text and other characters reliably.

// advantages

Why is UTF-8 so widely used?

Unicode support

It can represent the full range of Unicode code points.

ASCII compatible

Basic ASCII characters retain their original one-byte representation.

Efficient

Common English characters require only one byte, while additional bytes are used when necessary.

Portable

UTF-8 is supported across operating systems, programming languages, databases and web technology.

// where it appears

UTF-8 appears throughout modern computing

UTF-8 can be used with many text-based technologies and file formats.

TXT CSV XML JSON HTML CSS JavaScript APIs Databases Web Pages

// key idea

The file format and the encoding are different things

This is one of the most useful concepts to understand.

File format: describes how information is organised.

Character encoding: describes how the characters themselves are represented as bytes.

CSV = structure of the data UTF-8 = encoding of the characters

A CSV file can therefore be encoded using UTF-8. An XML document can be encoded using UTF-8. A plain .txt file can also be encoded using UTF-8.

// summary

Characters become bytes.

UTF-8 is a character encoding that converts Unicode characters into sequences of one to four bytes. It allows computers to store and exchange text from many languages, symbols and writing systems while remaining compatible with ASCII.

// file formats

What Is a .csv File?

A .csv file is a simple way of storing tabular data as plain text. It is commonly used to move information between spreadsheets, databases, websites and software applications.

// definition

CSV means Comma-Separated Values

CSV stands for Comma-Separated Values.

A .csv file stores data as plain text, usually with each line representing a row and commas separating the individual values within that row.

This makes CSV particularly useful for information that naturally fits into rows and columns.

// example

What does CSV data look like?

Imagine a spreadsheet containing customer information:

Name,Email,Orders Alice,alice@example.com,4 Ben,ben@example.com,7 Carla,carla@example.com,2

The first line contains the column headings. Each line after that represents one record.

Name	Email	Orders
Alice	alice@example.com	4
Ben	ben@example.com	7
Carla	carla@example.com	2

The CSV file and the table contain essentially the same information. The difference is how that information is represented.

// structure

Rows, columns and values

Rows

Each line normally represents one record, such as one customer, one product or one transaction.

Columns

Each position within a row represents a particular field, such as a name, price or date.

Delimiter

Commas normally separate the fields from one another, giving the format its name.

Header row

Many CSV files begin with a row containing the names of the columns, although this is not compulsory.

// plain text

A CSV file is still a text file

CSV is a structured text format.

If you open a CSV file in a plain-text editor, you can normally read its contents directly.

However, spreadsheet software such as Microsoft Excel or Google Sheets can interpret the separators and display the information as rows and columns.

Plain Text Rows Columns Records Fields

// quoted values

What happens if the data itself contains a comma?

Sometimes a value needs to contain a comma of its own. In that situation, the value can be enclosed in double quotation marks.

Name,Location Alice,"Birmingham, England" Ben,"London, England"

The quotation marks tell software that the comma inside the location belongs to the value rather than separating two different columns.

// escaping

What about quotation marks inside a value?

If a quoted field itself contains a double quotation mark, CSV commonly represents it by doubling the quotation mark.

Product,Description Book,"The ""Advanced"" Edition"

This allows the quotation mark to remain part of the actual data.

// csv vs spreadsheet

A CSV file is not an Excel workbook

Excel can open CSV files, but that does not make CSV an Excel format.

A normal Excel workbook can store much more than simple tabular values. It can contain formatting, formulas, multiple worksheets, charts and other spreadsheet features.

Feature	CSV	Excel workbook
Rows and columns	Yes	Yes
Plain text	Yes	No
Multiple worksheets	No	Yes
Cell formatting	No	Yes
Charts	No	Yes

Important: when an Excel workbook is exported to CSV, features such as colours, fonts, charts and multiple worksheets are not preserved as part of the CSV format.

// why csv?

Why is CSV so widely used?

Simple

CSV has a straightforward structure that is relatively easy for both people and software to understand.

Portable

CSV files can move data between many different applications and operating systems.

Lightweight

There is very little additional information surrounding the actual data.

Programmable

Programming languages and data tools can easily read, create and transform CSV files.

// uses

What are CSV files used for?

CSV files are common anywhere structured data needs to move from one system to another.

Customer Data Product Lists Transactions Website Data Analytics Database Exports Affiliate Data Inventory Spreadsheets Data Migration

// encoding

CSV and UTF-8

Like other text files, a CSV file must use a character encoding.

UTF-8 is a particularly useful choice because it supports a huge range of characters and languages.

Name,City,Amount João,Lisboa,£25 Élodie,Paris,€40 Sofia,Athens,€32

Important: the .csv extension does not itself guarantee UTF-8. The character encoding is a separate property of the file.

// delimiters

Is a comma always used?

CSV literally means Comma-Separated Values, and commas are the standard delimiter associated with the format.

In practice, however, data files may also use other separators. For example, semicolons are sometimes used because of regional settings or software conventions.

Name;City;Orders Alice;Birmingham;4 Ben;London;7

Files using tabs as separators are commonly called TSV, meaning Tab-Separated Values.

// data management

Why CSV matters in data management

CSV is particularly useful because it provides a simple bridge between different systems.

A database can export records to CSV. A spreadsheet can open them. A script can transform them. Another application can then import the resulting file.

Database ↓ CSV ↓ Spreadsheet ↓ Script / Automation ↓ Another System

This makes CSV extremely useful for data migration, cleaning, imports, exports and automation.

// txt vs csv

How is CSV different from TXT?

Both .txt and .csv files can contain plain text.

The key difference is that CSV normally follows a tabular structure: values are separated into fields and records so that software can interpret them as rows and columns.

A general .txt file does not necessarily have that structure.

Format	Main purpose
.txt	General plain-text information
.csv	Structured tabular data

// summary

Simple text. Structured data.

A .csv file stores tabular information as plain text, normally using commas to separate values and new lines to separate records. Its simplicity makes CSV one of the most useful formats for exchanging data between spreadsheets, databases, websites and software systems.