What ASCII is
ASCII is the 7-bit encoding that maps the numbers 0 through 127 to the basic Latin letters, digits, punctuation, and a set of control characters. It is the historical foundation of digital text and the first 128 code points of Unicode.
How it works
The lookup accepts three input styles. A bare number like 65 is read as a decimal code; a value prefixed with 0x such as 0x41 is read as hexadecimal; and a single typed character is matched to its own code. The tool validates that the result lands in the ASCII range 0–127 and then highlights that row in the full table.
Each row shows the same code in four bases — decimal, hexadecimal, octal, and binary — so you can read whichever your task needs. Control characters (0–31 and 127) cannot be displayed as glyphs, so the table substitutes their standard abbreviations such as NUL, HT (tab), LF (newline), and DEL.
Example and notes
Looking up 65, 0x41, or A all land on the same row: the letter A, hex 0x41, octal 101, binary 01000001. The space character is code 32, the digit 0 is code 48, and DEL is code 127.
A useful pattern: uppercase and lowercase letters differ by exactly 32, so A (65) and a (97) sit a fixed distance apart — clearing or setting that one bit toggles letter case. Codes above 127 fall outside ASCII; reach for the Unicode-aware tools when you need them.