What is the difference between Big-Endian and Little-Endian in UTF-16 and UTF-32?

Endianness refers to the byte order used to store multi-byte numbers in computer memory. In Little-Endian (LE), the least significant byte is stored first at the lowest memory address (common in x86/ARM processors). In Big-Endian (BE), the most significant byte is stored first (traditional network byte order). For example, "A" (U+0041) in UTF-16LE is 41 00, while in UTF-16BE it is 00 41.

Why does UTF-8 not have endianness variations?

UTF-8 serializes code points as a sequential stream of 8-bit bytes rather than 16-bit or 32-bit integers. Because each unit is exactly one byte, byte-order memory differences between CPU architectures do not apply.

What is a Byte Order Mark (BOM U+FEFF) used for?

A Byte Order Mark is a special Unicode signature placed at the beginning of a file. When a reader reads FE FF, it knows the file is UTF-16BE; if it reads FF FE, it knows the file is UTF-16LE.

Tools/UTF Endianness Inspector

UTF Endianness & Raw Byte Serialization Inspector

Inspect, compare, and convert text across all 5 standard Unicode serialization formats: UTF-8, UTF-16LE, UTF-16BE, UTF-32LE, and UTF-32BE with optional Byte Order Mark (BOM) inclusion.

Include Byte Order Mark (BOM Header U+FEFF)

Unicode 🚀

UTF-8 (Web Standard)

Width: 1–4 BytesEndianness: N/A (Byte Stream)

55 6E 69 63 6F 64 65 20 F0 9F 9A 80

Backward-compatible with ASCII. Uses 1 byte for ASCII, 2 for Latin/Greek, 3 for CJK/Arabic, 4 for emojis.

UTF-16LE (Little-Endian)

Width: 2 or 4 BytesEndianness: Least Significant First

55 00 6E 00 69 00 63 00 6F 00 64 00 65 00 20 00 3D D8 80 DE

Default in Windows NT kernel, JavaScript V8 string memory, and Java JVM.

UTF-16BE (Big-Endian)

Width: 2 or 4 BytesEndianness: Most Significant First

00 55 00 6E 00 69 00 63 00 6F 00 64 00 65 00 20 D8 3D DE 80

Standard Network Byte Order for UTF-16 transmission in legacy protocols.

UTF-32LE (Fixed 4-Byte)

Width: 4 Bytes (Fixed)Endianness: Least Significant First

55 00 00 00 6E 00 00 00 69 00 00 00 63 00 00 00 6F 00 00 00 64 00 00 00 65 00 00 00 20 00 00 00 80 F6 01 00

Direct 1-to-1 array indexing for every code point in memory without surrogate pairs.

UTF-32BE (Fixed 4-Byte)

Width: 4 Bytes (Fixed)Endianness: Most Significant First

00 00 00 55 00 00 00 6E 00 00 00 69 00 00 00 63 00 00 00 6F 00 00 00 64 00 00 00 65 00 00 00 20 00 01 F6 80

Fixed 32-bit dwords serialized with most-significant byte first.

Character-by-Character Byte Breakdown (9 Glyphs)

Anatomical inspection of each code point with its individual UTF-8 byte stream and UTF-16 LE/BE encodings.

Glyph	Codepoint	UTF-8 Hex	UTF-16LE	UTF-16BE	UTF-32LE
U	U+0055	55	55 00	00 55	55 00 00 00
n	U+006E	6E	6E 00	00 6E	6E 00 00 00
i	U+0069	69	69 00	00 69	69 00 00 00
c	U+0063	63	63 00	00 63	63 00 00 00
o	U+006F	6F	6F 00	00 6F	6F 00 00 00
d	U+0064	64	64 00	00 64	64 00 00 00
e	U+0065	65	65 00	00 65	65 00 00 00
	U+0020	20	20 00	00 20	20 00 00 00
🚀	U+1F680	F0 9F 9A 80	3D D8 80 DE	D8 3D DE 80	80 F6 01 00

The Engineering Science of UTF Serialization & CPU Endianness

In computer architecture, endianness refers to the order in which bytes of a multi-byte word are stored in computer memory. The terms originate from Jonathan Swift’s Gulliver’s Travels, where rival factions fought over whether soft-boiled eggs should be cracked from the larger end (Big-Endian) or smaller end (Little-Endian).

When serializing 16-bit (UTF-16) or 32-bit (UTF-32) Unicode integers, the byte order matters critically:

• Little-Endian (LE): Least Significant Byte (LSB) first — native to Intel x86, AMD64, Apple Silicon (ARM), Windows NT, and JavaScript V8.

• Big-Endian (BE): Most Significant Byte (MSB) first — native to traditional TCP/IP Network Byte Order and mainframe architectures.

UTF-8, by contrast, encodes characters as an 8-bit stream of bytes. Because every encoding unit is already a single byte, UTF-8 is completely immune to endianness issues and does not require a BOM header.

Byte Order Mark (BOM U+FEFF) Signatures Matrix

UTF-8 BOM:EF BB BF

UTF-16 Little-Endian:FF FE

UTF-16 Big-Endian:FE FF

UTF-32 Little-Endian:FF FE 00 00

Frequently Asked Questions (FAQs)

Why does Windows Notepad add a UTF-8 BOM by default?+

Legacy versions of Windows Notepad used the EF BB BF byte signature to distinguish UTF-8 text from Windows-1252 ANSI. Modern standards recommend omitting BOM in UTF-8 to prevent shell script execution failures.

How does UTF-32 provide O(1) constant-time character indexing?+

Because every single Unicode code point in UTF-32 consumes exactly 4 bytes (32 bits), accessing character at index N is a simple pointer calculation: buffer + (N * 4).

Can I copy raw hex bytes directly into C/C++ or Rust code?+

Yes! Click the "Copy Hex Bytes" button next to any encoding to copy formatted hex sequences for uint8_t arrays or buffer initialization.