Difference Between UTF-8 and UTF-16

The encoding techniques UTF-8 and UTF-16 are both used to represent characters from the Unicode character set. They are commonly used to manage text in many scripts and languages in computer systems and programming languages.

Read this article to find out more about UTF-8 and UTF-16 and how they are different from each other.

What is UTF-8?

UTF-8 (Unicode Transformation Format-8) is a character encoding system with varying lengths that is extensively used to represent Unicode characters. It has been developed to be ASCII (American Standard Code for Information Interchange) compatible while also supporting the whole Unicode character set.

Encoding Scheme

UTF-8 represents characters with 8-bit units (bytes), making it backward compatible with ASCII. The first 128 Unicode code points (U+0000 to U+007F) are represented by a single byte, just as the corresponding ASCII characters are.

Encoding Rules

ASCII codes (from U+0000 to U+007F): They are represented by a single byte, which is identical to their ASCII representation (7 bits).

Supplement to Latin-1 (U+0080 to U+07FF): Two bytes are used to represent it.

Characters in the Basic Multilingual Plane (BMP) (U+0800 to U+FFFF): Three bytes are used to represent it.

Byte Structure

• The most significant bit (MSB) is always zero, and the remaining 7 bits reflect the code point of the character.

• To distinguish them from ASCII characters, the most significant bits of each byte are set to 1, and the consecutive bytes begin with the prefix "10".

What is UTF-16?

UTF-16 is a character encoding system which uses 16-bit code to encode Unicode characters. It was created to handle the increasing requirement for compact and effective representation of a diverse range of characters, including additional characters.

Encoding Scheme

• UTF-16 uses 16-bit code units that are either 2 or 4 bytes long to represent characters.

• 2-byte code units are used to represent Basic Multilingual Plane (BMP) characters, which include the most regularly used characters.

• Supplementary characters, or characters that exist outside of the BMP, are represented by a pair of 2-byte code units known as surrogate pairs, totaling 4 bytes.

Encoding Rules

• Unicode characters with code points ranging from U+0000 to U+FFFF: These characters are directly represented by a single 2-byte code unit. The code unit value corresponds to the character's code point.

• Additional characters with code points ranging from U+10000 to U+10FFFF: Surrogate pairs, which comprise two 2-byte code units, are used to represent these characters.

Byte Order

• UTF-16 can have different byte orders, which are referred to as byte order markers (BOM). Big endian (BE) or little endian (LE) byte order is supported.

• A BOM is a special character (U+FEFF) that indicates the byte order at the beginning of the text.

Benefits

• Characters in BMP can be represented by a single 2-byte code unit, making text indexing and manipulation easier.

• UTF-16 supports additional characters through surrogate pairs, allowing for the representation of a large range of characters.

• UTF-16 is used as the internal encoding of many programming languages, frameworks, and operating systems, making it well-suited for interoperability.

For handling Unicode text, UTF-16 is extensively used in many programming languages (such as Java and C#) and operating systems (such as Windows). It allows for the effective storage of characters in BMP files and the representation of supplemental characters when required.

Difference between UTF-8 and UTF-16

The following table highlights the major differences between UTF-8 and UTF-16 −

Characteristics	UTF-8	UTF-16
Byte Order	Byte order is not relevant	Can have different byte orders (big endian or little endian)
Character Representation	Characters represented by a sequence of bytes	Characters represented by 16-bit code units
Supported Characters	Supports the entire Unicode character set	Supports the entire Unicode character set, including supplementary characters
Usage	used for web, email, and storage systems	used in programming languages and operating systems
Encoding Scheme	Variable-length encoding scheme	Fixed-length encoding scheme (2 or 4 bytes)
Memory Usage	Requires less memory, especially for ASCII-based texts	Requires more memory, especially for non-ASCII and supplementary characters

Conclusion

The decision between UTF-8 and UTF-16 depends on the system's or application's specific requirements. UTF-8 is widely used for ASCII compatibility and is more memory-efficient for ASCII-based content. When a wider range of Unicode characters, including additional characters, must be handled, UTF-16 is frequently used.