ASCII and Unicode Lookup

This is the kind of tool you don't need until 2am, and then you need it badly. Something's printing a stray character in a log file, a CSV import is silently mangling line endings, or you're trying to remember whether a tab is decimal 9 or 11 for the tenth time this year. Type a character in and get every representation back at once — decimal, hex, binary, Unicode code point, HTML entity — instead of tabbing between three reference sites.

The part everyone half-remembers

ASCII only ever defined 128 characters (0–127), which is why it fits in 7 bits with room to spare. The first 32 (plus 127) aren't printable at all — they're control codes left over from teletype days, and a surprising number of them still matter: tab is 9, line feed is 10, carriage return is 13, escape is 27. If you've ever opened a Windows text file on Linux and seen ^M at the end of every line, that's CR (13) showing up where a Unix tool only expected LF (10).

Where this actually bites people

• Line ending mismatches between Windows (CRLF) and Unix (LF) — breaks shell scripts with a mysterious "command not found" on the very first line
• CSV files that look fine in Excel but fail to parse because of an invisible byte-order mark (U+FEFF) at the start
• Copy-pasting from Word or Google Docs and getting "smart quotes" (U+2018/2019) instead of plain ASCII apostrophes, which then breaks a shell script or JSON string
• Legacy systems that still assume Latin-1 encoding choking on anything outside the first 256 code points

ASCII, Unicode, UTF-8 — not the same thing

ASCII is the original 128-character set. Unicode is the much bigger standard (over 140,000 characters covering every writing system, plus emoji) that assigns every character a code point. UTF-8 is one way of encoding those code points as bytes — and it was deliberately designed so the first 128 code points map to the exact same bytes as ASCII. That's why a plain English text file is valid in both encodings simultaneously, and why UTF-8 won: it's backward compatible with four decades of ASCII-only software without anyone having to change anything.