代理对

Encoding & Standards

用于表示U+FFFF以上字符的两个UTF-16编码单元组合，由高代理（U+D800-U+DBFF）和低代理（U+DC00-U+DFFF）构成。

Characters with code points above U+FFFF cannot fit in a single 16-bit value. UTF-16 solves this by encoding them as two 16-bit values called a surrogate pair. Since most emoji are above U+FFFF, surrogate pairs are extremely common with emoji.

For example, 😀 (U+1F600) becomes the surrogate pair 0xD83D 0xDE00 in UTF-16. The formula: high surrogate = 0xD800 + ((cp - 0x10000) >> 10), low surrogate = 0xDC00 + ((cp - 0x10000) & 0x3FF).

This is why JavaScript's `'😀'.charCodeAt(0)` returns 55357 (0xD83D) — it's returning the high surrogate, not the actual code point.

相关术语

UTF-16 UTF-16
每字符使用2或4个字节的可变长度Unicode编码方式，被JavaScript、Java和Windows内部使用。 平面 平面
由65,536个连续Unicode码位构成的分组。第0平面为基本多文种平面（BMP），大多数表情符号位于第1平面（SMP）。 编码单元 编码单元
用于编码字符的最小位组合：UTF-8为8位，UTF-16为16位，UTF-32为32位。 补充多文种平面（SMP） (SMP) 补充多文种平面（SMP） (SMP)
Unicode第1平面（U+10000至U+1FFFF），绝大多数表情符号码位都分配在此区域。

相关工具

🔢 Unicode 查询 Unicode 查询
输入 U+1F600 等码位，获取表情符号、编码详情、UTF-8/16 字节和 HTML 实体。 🔍 序列分析器 序列分析器
将 ZWJ 序列、肤色修饰符、键帽序列和旗帜对解析为独立组成部分。

相关故事

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 — UTF-8, UTF-16, HTML entities, and more.
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.
Handling Emojis in JSON and REST APIs
How to correctly handle emoji in JSON serialization, REST API design, database storage, and HTTP headers — including surrogate pair pitfalls.
Emoji Encoding Guide: UTF-8, UTF-16 & Surrogate Pairs
A developer's guide to emoji encoding — how UTF-8, UTF-16, and UTF-32 represent emoji, and common pitfalls with surrogate pairs.