ASCII 91
Left Square Bracket ([)
Printable ASCII
Left square bracket. Opens array literals and index accesses.
Common uses & context
The character '[' — Left Square Bracket — has ASCII code 91 (0x5B), octal 0133, binary 01011011. Left square bracket. Opens array literals and index accesses.
Punctuation and symbol codes carry the most syntactic weight per byte in programming: a single '[' can change how a parser reads an entire expression. When '[' needs to appear as literal data rather than syntax, you often have to escape it — in string literals, in regular expressions, in URLs (where it becomes %5B), or in HTML. Knowing its exact code point (91) helps when you filter, validate, or sanitize input byte by byte.
All encodings at a glance
| Decimal | 91 |
| Hexadecimal | 0x5B |
| Octal | 0133 |
| Binary | 01011011 |
| HTML numeric entity | [ |
| URL encoding | %5B |
| UTF-8 bytes | 0x5B |
Code snippets
JavaScript
String.fromCharCode(91); // "["
91.toString(16); // "5b"Python
chr(91) # '['
ord(chr(91)) # 91
hex(91) # '0x5b'HTML
[ <!-- numeric entity (no named entity for this character) -->Programming notes
- ▸Code 91 (0x5B); URL-encoded form%5B.
- ▸In HTML the numeric entity is [.
- ▸When used as literal data in regex or strings, '[' usually needs escaping — check the rules for your language.
Frequently asked questions
What character is ASCII code 91?
ASCII code 91 is the character '[' (Left Square Bracket). In hexadecimal it is 0x5B, in octal 0133, and in binary 01011011.
What is 0x5B in ASCII?
Hexadecimal 0x5B equals decimal 91, which is the character '[' (Left Square Bracket). To convert hex to ASCII yourself, read the two hex digits as a base-16 number (0x5B = 91) and look up that code point.
How do I write the character with code 91 in code?
In JavaScript use String.fromCharCode(91); in Python use chr(91); in HTML use the numeric entity [. In a URL it is percent-encoded as %5B, and in UTF-8 it is stored as the byte sequence 0x5B.