Introduction

hangul.dev is a technical reference for working with Hangul (Korean script) in software. This documentation covers Unicode encoding, syllable composition algorithms, jamo decomposition, and practical code examples for processing Korean text.

Hangul is one of the most systematically designed writing systems in the world. Created in 1443 by King Sejong the Great, its structure maps directly to computational models: consonants and vowels (jamo) compose into syllable blocks following strict rules that are elegantly represented in Unicode.

Key Concept: In Unicode, Hangul syllable characters (가-힣) are algorithmically composed from three components: an initial consonant (choseong), a medial vowel (jungseong), and an optional final consonant (jongseong).

Hangul Basics

Consonants (자음)

Hangul has 14 basic consonants, each depicting the shape of the speech organ used to produce it. Additional consonants are formed by adding strokes to these base forms.

ㄱ ㄴ ㄷ ㄹ ㅁ ㅂ ㅅ ㅇ ㅈ ㅊ ㅋ ㅌ ㅍ ㅎ

Vowels (모음)

Hangul vowels are constructed from three philosophical elements: a dot (heaven), a horizontal line (earth), and a vertical line (humanity). These combine to form 10 basic vowels.

ㅏ ㅑ ㅓ ㅕ ㅗ ㅛ ㅜ ㅠ ㅡ ㅣ

Unicode Overview

Hangul characters occupy several blocks in the Unicode Standard:

Block Range Count Description
Hangul Jamo U+1100..U+11FF 256 Conjoining jamo for algorithmic composition
Hangul Compatibility Jamo U+3130..U+318F 96 Standalone jamo for display
Hangul Syllables U+AC00..U+D7AF 11,172 Precomposed syllable characters
Hangul Jamo Extended-A U+A960..U+A97F 32 Old Korean initial consonants
Hangul Jamo Extended-B U+D7B0..U+D7FF 80 Old Korean vowels and final consonants

Jamo Block

Initial Consonants (Choseong)

The 19 initial consonants used in syllable composition, indexed 0-18:

Medial Vowels (Jungseong)

The 21 medial vowels used in syllable composition, indexed 0-20:

Final Consonants (Jongseong)

The 28 final consonant positions (index 0 = no final), indexed 0-27:

Syllable Composition

The Unicode Hangul Syllable Composition algorithm computes a syllable character from its jamo components using a simple formula:

Formula 
syllable = 0xAC00 + (initial * 21 + medial) * 28 + final

where:
  initial = index of choseong  (0-18)
  medial  = index of jungseong (0-20)
  final   = index of jongseong (0-27, 0 = none)

Example: Composing 한

한 U+D55C
←
ㅎ initial (18)
+
ㅏ medial (0)
+
ㄴ final (4)
Calculation 
0xAC00 + (18 * 21 + 0) * 28 + 4
= 0xAC00 + (378) * 28 + 4
= 0xAC00 + 10584 + 4
= 0xAC00 + 0x2958 + 0x4
= 0xD55C
= 한

Decomposition

To decompose a Hangul syllable character back into its jamo components, reverse the composition formula:

JavaScript 
function decomposeHangul(syllable) {
    const code = syllable.charCodeAt(0) - 0xAC00;
    if (code < 0 || code > 11171) return null;

    const initial = Math.floor(code / (21 * 28));
    const medial = Math.floor((code % (21 * 28)) / 28);
    const final_ = code % 28;

    const CHOSEONG = [
        'ㄱ','ㄲ','ㄴ','ㄷ','ㄸ','ㄹ','ㅁ','ㅂ','ㅃ',
        'ㅅ','ㅆ','ㅇ','ㅈ','ㅉ','ㅊ','ㅋ','ㅌ','ㅍ','ㅎ'
    ];
    const JUNGSEONG = [
        'ㅏ','ㅐ','ㅑ','ㅒ','ㅓ','ㅔ','ㅕ','ㅖ','ㅗ','ㅘ',
        'ㅙ','ㅚ','ㅛ','ㅜ','ㅝ','ㅞ','ㅟ','ㅠ','ㅡ','ㅢ','ㅣ'
    ];
    const JONGSEONG = [
        '','ㄱ','ㄲ','ㄳ','ㄴ','ㄵ','ㄶ','ㄷ','ㄹ','ㄺ',
        'ㄻ','ㄼ','ㄽ','ㄾ','ㄿ','ㅀ','ㅁ','ㅂ','ㅄ','ㅅ',
        'ㅆ','ㅇ','ㅈ','ㅊ','ㅋ','ㅌ','ㅍ','ㅎ'
    ];

    return {
        initial: CHOSEONG[initial],
        medial: JUNGSEONG[medial],
        final: JONGSEONG[final_] || null
    };
}

Try it: Interactive Decomposition

Character Explorer

Browse all 11,172 Hangul syllable characters (U+AC00 to U+D7A3). Click any character to decompose it.

Showing 가 (U+AC00) to 힣 (U+D7A3)

Code Examples

Check if a character is Hangul

function isHangulSyllable(char) {
    const code = char.charCodeAt(0);
    return code >= 0xAC00 && code <= 0xD7A3;
}

function isHangulJamo(char) {
    const code = char.charCodeAt(0);
    return (code >= 0x1100 && code <= 0x11FF) ||
           (code >= 0x3130 && code <= 0x318F);
}

isHangulSyllable('한');  // true
isHangulSyllable('A');   // false

Count Hangul characters in a string

function countHangul(str) {
    return [...str].filter(ch => {
        const code = ch.charCodeAt(0);
        return code >= 0xAC00 && code <= 0xD7A3;
    }).length;
}

countHangul('Hello 세계!');  // 2

API Reference

Constants

Name Value Description
HANGUL_BASE 0xAC00 Start of Hangul Syllables block (가)
HANGUL_END 0xD7A3 End of Hangul Syllables block (힣)
CHOSEONG_COUNT 19 Number of initial consonants
JUNGSEONG_COUNT 21 Number of medial vowels
JONGSEONG_COUNT 28 Number of final consonant positions (including none)

Functions

TypeScript 
interface HangulComponents {
    initial: string;   // Choseong jamo
    medial: string;    // Jungseong jamo
    final: string | null; // Jongseong jamo or null
}

function decompose(syllable: string): HangulComponents | null;
function compose(initial: number, medial: number, final?: number): string;
function isHangulSyllable(char: string): boolean;
function isHangulJamo(char: string): boolean;
function getCharacterName(char: string): string;