Legacy Encoding Survival Guide: From ASCII to GB18030
A practical overview of 20+ character encodings across languages, how they relate, and how to identify them.
The Encoding Family Tree
Before Unicode, every language needed its own encoding. The result was a tangled tree of standards, each solving the same problem differently:
| Era | Encoding | Characters |
|---|---|---|
| 1963 | ASCII | 128 (English only) |
| 1987 | ISO 8859-1 (Latin-1) | 256 (Western European) |
| 1990s | Windows code pages | 256 per page (regional) |
| 1978+ | CJK double-byte | 6,000-20,000 (East Asian) |
| 1991+ | Unicode (UTF-8/16) | 150,000+ (all languages) |
This tool shows encoding bytes for 20+ legacy encodings simultaneously, letting you compare how the same character is represented across different systems.
Single-Byte Encodings
Single-byte encodings map each byte (0x00-0xFF) to one character. They share ASCII in the lower half (0x00-0x7F) but differ in the upper half (0x80-0xFF):
| Encoding | Region | Upper half contains | |
|---|---|---|---|
| ISO 8859-1 / Latin-1 | Western Europe | àáâãäå, ñ, ü, ß, etc. | |
| Windows-1252 | Western Europe | Same + €, | , —, etc. |
| ISO 8859-2 | Central Europe | ą, ć, č, ě, ł, ő, ž, etc. | |
| Windows-1251 | Cyrillic | А-Я, а-я, etc. | |
| KOI8-U | Ukrainian | Cyrillic (different order) | |
| ISO 8859-7 | Greek | Α-Ω, α-ω, etc. |
WHATWG treats iso-8859-1 as windows-1252. Bytes 0x80-0x9F that are C1 controls in ISO 8859-1 become typographic characters (€, ", —) in Windows-1252.
East Asian Double-Byte Encodings
CJK languages need thousands of characters, requiring multi-byte encodings:
| Encoding | Language | Standard |
|---|---|---|
| Shift_JIS / CP932 | Japanese | JIS X 0208 / Windows-31J |
| EUC-JP | Japanese | JIS X 0208 (Unix) |
| ISO-2022-JP | Japanese | JIS X 0208 (Email) |
| Big5 | Chinese (Traditional) | Taiwan standard |
| GBK / GB18030 | Chinese (Simplified) | China standard |
| EUC-KR (CP949) | Korean | KS X 1001 / UHC |
The same CJK character gets completely different byte sequences in each encoding. This tool shows them all side by side.
Auto-Detection: How the Tool Picks Encodings
This tool automatically detects which encoding groups are relevant for each character using two methods:
For CJK characters: The Unihan IRG Source database (88,000+ characters) identifies which national standards include each character. This is more accurate than simple encoding checks.
For other scripts: Encodability checks against the broadest encoding in each group (e.g., Windows-1252 for Western, Windows-1251 for Cyrillic).
Related articles
Shift_JIS vs CP932: The Encoding Everyone Confuses
The precise technical differences between Shift_JIS and CP932 (Windows-31J), with byte-level evidence.
The Wave Dash Problem: 〜 vs ～ and 7 Other Mapping Conflicts
Complete reference on the 7 JIS-Unicode mapping discrepancies with an interactive toggle to see both variants.