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What Is a Unicode Block?

A Unicode block is a named, contiguous range of code points assigned to a related group of characters. The Unicode Standard divides the entire code point space (U+0000 to U+10FFFF) into 336 blocks, each a multiple of 16 code points in size. Block boundaries are fixed—they never change between Unicode versions—though new blocks may be allocated in previously unassigned ranges.

Each block has a distinctive name that broadly describes its contents: Basic Latin (U+0000–U+007F), Greek and Coptic (U+0370–U+03FF), or CJK Unified Ideographs (U+4E00–U+9FFF). The name is informational rather than prescriptive, so a block may contain characters from multiple scripts, or even unassigned code points.

Blocks vs. Scripts

Blocks are purely positional: a character belongs to exactly one block based on its numeric value. Scripts, by contrast, reflect linguistic or cultural affiliation. The Latin Extended Additional block (U+1E00–U+1EFF) contains Latin characters, but the Letterlike Symbols block (U+2100–U+214F) holds characters from many scripts such as ℂ (DOUBLE-STRUCK CAPITAL C) and ℓ (SCRIPT SMALL L). A single block can span multiple scripts, and one script can span multiple blocks.

import unicodedata

# Look up the block of a character using the Unicode data utilities
# Python's unicodedata module does not expose block directly,
# but you can derive it from the character name prefix or use the
# 'unicode_data' third-party package.

for char in ["A", "α", "中", "😀"]:
    name = unicodedata.name(char, "<unnamed>")
    cp = ord(char)
    print(f"U+{cp:04X}  {char}  {name}")

# U+0041  A  LATIN CAPITAL LETTER A       → Basic Latin
# U+03B1  α  GREEK SMALL LETTER ALPHA     → Greek and Coptic
# U+4E2D  中 CJK UNIFIED IDEOGRAPH-4E2D   → CJK Unified Ideographs
# U+1F600 😀 GRINNING FACE                → Emoticons

Why Blocks Matter

Blocks appear in Unicode Character Ranges used by CSS (@font-face unicode-range), regular expressions (\p{Block=CJK_Unified_Ideographs} in Perl, PCRE, or Java), and font subsetting tools. Knowing a character's block helps font engineers decide which code-point ranges to include in a subset, reducing file size while preserving coverage.

Block assignments also guide rendering engines. For example, shaping engines like HarfBuzz use block membership as one heuristic when selecting a shaping script when no explicit script tag is available.

Quick Facts