UTF-16

Encoding & Standards

A variable-width Unicode encoding that uses 2 or 4 bytes per character, used internally by JavaScript, Java, and Windows.

UTF-16 uses 16-bit code units. Characters in the Basic Multilingual Plane (U+0000 to U+FFFF) use one code unit (2 bytes). Characters above U+FFFF โ€” including most emoji โ€” require a surrogate pair (4 bytes).

This is why JavaScript's `string.length` can be surprising with emoji: `'๐Ÿ˜€'.length` returns 2 (two UTF-16 code units), not 1. Developers must use spread syntax (`[...'๐Ÿ˜€'].length`) or `Array.from()` for correct counting.

UTF-16 exists in two byte orders: UTF-16LE (little-endian, used by Windows) and UTF-16BE (big-endian). A BOM character can indicate which is used.

Related Terms

BOM (BOM) BOM (BOM)
The Byte Order Mark (U+FEFF) placed at the start of a text file to indicate byte order (endianness) in UTF-16/UTF-32 encodings. Code Unit Code Unit
The minimum bit combination used for encoding a character: 8-bit for UTF-8, 16-bit for UTF-16, and 32-bit for UTF-32. Supplementary Multilingual Plane (SMP) Supplementary Multilingual Plane (SMP)
Unicode Plane 1 (U+10000 to U+1FFFF), where the majority of emoji code points are allocated. Surrogate Pair Surrogate Pair
Two UTF-16 code units (a high surrogate U+D800-U+DBFF followed by a low surrogate U+DC00-U+DFFF) that together represent a character above U+FFFF. UTF-32 UTF-32
A fixed-width Unicode encoding that uses exactly 4 bytes per character, providing direct code point mapping at the cost of space. UTF-8 UTF-8
A variable-width Unicode encoding that uses 1 to 4 bytes per character, dominant on the web (used by 98%+ of websites).

Related Tools

๐Ÿ”ข Unicode Lookup Unicode Lookup
Enter a codepoint like U+1F600 and get the emoji, encoding details, UTF-8/16 bytes, and HTML entities.

Related Stories

Unicode Lookup: Find Any Emoji by Code Point
Enter a Unicode code point like U+1F600 or paste an emoji to see its full encoding breakdown โ€” UTF-8, UTF-16, HTML entities, and more.
What Are ZWJ Sequences? How Emoji Combine
Learn how Zero Width Joiner (ZWJ) sequences combine multiple emoji into one โ€” from family emoji to professions to flags.
Emoji Sequence Analyzer: Decode ZWJ, Skin Tones, and Keycaps
Learn how to use EmojiFYI's Sequence Analyzer to break down ZWJ sequences, skin tone modifiers, keycap sequences, and flag emojis into their Unicode components.
How to Handle Emojis in JavaScript: Strings, Length, and Rendering
Learn how to work with emojis in JavaScript: string length pitfalls, Unicode code points, regex, grapheme segmentation, and React rendering tips.
Why string.length Lies: Grapheme Clusters and Emoji Length
Why string.length fails for emoji, what grapheme clusters are, and how to correctly count characters in JavaScript, Python, and more.
EmojiFYI Developer Tools: A Complete Overview
Explore all six EmojiFYI interactive tools built for developers: compare platforms, analyze sequences, access the API, convert text, and more.