ASCII table explorer
All 128 ASCII codes in every notation, with their names from RFC 20 to Unicode 18.0.0, how to write each one in C, JSON, JavaScript, Python, Tcl, HTML and URLs, and a look-up that tells you when a character is not ASCII at all.
编码与数据Reads decimal, hexadecimal (0x41 or 41h), octal (0o101), seven or eight binary digits, RFC 20 column/row (4/11), U+0041, HTML references, percent-encoding, backslash escapes, caret notation, control abbreviations and names, Unicode names, or the character itself.
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Code 65 0x41 · U+0041
LATIN CAPITAL LETTER A
Read as: the character itself
Numbers
- Decimal
65- Hexadecimal
0x41- Octal
0o101- Binary (7 bits)
1000001- In a byte (8 bits)
01000001- Column/row (RFC 20)
4/1Bits b7 b6 b5 give the column, b4 to b1 the row.
Flip a bit
Each button flips one bit and jumps to the code it lands on. b6 (value 32) separates upper and lower case; b7 (value 64) separates a control from the character it is paired with in caret notation.
Names
- Unicode 18.0.0
LATIN CAPITAL LETTER A- General_Category
LuUppercase_Letter- RFC 20 class
- Graphic character.
Relations
- Other case
a, one bit away: upper and lower case differ only in b6 (value 32).
White space?
- C isspace() no
- JSON (RFC 8259) no
- WHATWG (HTML, URLs) no
- ABNF WSP (RFC 5234) no
- Tcl 8.4 word separator no
- Python str.isspace() no
- JavaScript \s and trim() no
Which definitions count this code as white space, measured in each implementation on 2026-10-03.
How to write it
Inside a string literal of each language, or in HTML and a URL.
| C | A | as itself |
|---|---|---|
| JSON | A | as itself |
| JavaScript | A | as itself |
| Python | A | as itself |
| Tcl and iRules | A | as itself |
| HTML, decimal | A | |
| HTML, hexadecimal | A | |
| HTML, named | none | |
| URL | %41 | Unreserved in RFC 3986: it never needs percent-encoding. |
The table
Laid out as RFC 20 draws it: eight columns by sixteen rows. Pick a code to see it above.
| b7 b6 b5b4 b3 b2 b1 | 0000 | 1001 | 2010 | 3011 | 4100 | 5101 | 6110 | 7111 |
|---|---|---|---|---|---|---|---|---|
| 00000 | ||||||||
| 10001 | ||||||||
| 20010 | ||||||||
| 30011 | ||||||||
| 40100 | ||||||||
| 50101 | ||||||||
| 60110 | ||||||||
| 70111 | ||||||||
| 81000 | ||||||||
| 91001 | ||||||||
| 101010 | ||||||||
| 111011 | ||||||||
| 121100 | ||||||||
| 131101 | ||||||||
| 141110 | ||||||||
| 151111 |
Text to codes
White space, compared
The same ten codes, seven definitions. JSON leaves out VT and FF, WHATWG leaves out VT, Tcl ends a command at LF instead of separating words, and Python also counts the four information separators.
| 9 | 10 | 11 | 12 | 13 | 28 | 29 | 30 | 31 | 32 | |
|---|---|---|---|---|---|---|---|---|---|---|
| C isspace() | yes | yes | yes | yes | yes | no | no | no | no | yes |
| JSON (RFC 8259) | yes | yes | no | no | yes | no | no | no | no | yes |
| WHATWG (HTML, URLs) | yes | yes | no | yes | yes | no | no | no | no | yes |
| ABNF WSP (RFC 5234) | yes | no | no | no | no | no | no | no | no | yes |
| Tcl 8.4 word separator | yes | no | yes | yes | yes | no | no | no | no | yes |
| Python str.isspace() | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes |
| JavaScript \s and trim() | yes | yes | yes | yes | yes | no | no | no | no | yes |
参考
- RFC 20: ASCII format for Network Interchange (V. Cerf, 1969), reproducing USAS X3.4-1968
- Unicode Character Database 18.0.0: UnicodeData.txt
- Unicode Character Database 18.0.0: PropList.txt
- Unicode Character Database 18.0.0: DerivedCoreProperties.txt
- Unicode Character Database 18.0.0: NameAliases.txt
- Unicode Character Database 18.0.0: extracted/DerivedName.txt
- Unicode Standard Annex #44: Unicode Character Database (revision 38, Unicode 18.0.0)
- WHATWG HTML Living Standard: named character references (entities.json)
- WHATWG HTML Living Standard: 13.2 Parsing HTML documents (numeric character reference end state)
- WHATWG Infra Standard: ASCII whitespace
- ISO/IEC 9899:2011 committee draft N1570 (C11): 6.4.4.4 escape sequences, 7.4.1.10 isspace
- RFC 8259: The JavaScript Object Notation (JSON) Data Interchange Format
- ECMA-262: ECMAScript Language Specification (string literals, white space, line terminators)
- The Python Language Reference: 2. Lexical analysis (escape sequences)
- Tcl 8.4 manual: Tcl (the twelve rules of the language, backslash substitution)
- RFC 3986: Uniform Resource Identifier (URI): Generic Syntax
- RFC 5234: Augmented BNF for Syntax Specifications: ABNF (Appendix B.1 core rules)