Control characters
C0 CONTROL CHARACTERS (U+0000–U+001F)
The 32 ASCII control codes — NUL, BEL, ESC, the file and record separators, and the rest. They are commands to a teletype, not text.
- Range
U+0000–U+001F- Category
- Control characters
- Removed by default
- No
- Governing option
- Control characters
--controls - Can be load-bearing
- No
Where it comes from
Binary data pasted as text, terminal output that still contains escape sequences, log files, mis-decoded files, and payloads that exploit software which handles them badly.
Why it matters
A NUL truncates a C string; an ESC can start a terminal escape sequence that changes what you see; the separators split records in unexpected places. Most of them render as nothing or as a placeholder box, so a reviewer sees a gap.
Before and after
U+0007 BELL — a character that used to ring a physical bell, now invisible.
The character is shown as a labelled chip so you can see where it sits. In your text it draws nothing at all.
When it is legitimate
Tab, line feed and carriage return, which is exactly why Ghostchars excludes those three from this group and never removes them.
How to remove it
Turn on Control characters (`--controls`). Tab, LF and CR are never touched; CR is handled separately by the line-ending pass.
Is it an AI watermark?
Not a watermark
No. Control characters in text mean a decoding problem or a deliberate probe. No model produces them as prose.
No connection to machine-generated text. It comes from software, from a keyboard, or from a person.
Questions
Does it remove tabs?
No. Tab (U+0009), line feed (U+000A) and carriage return (U+000D) are excluded from this group. Line endings are handled by `-n`.
Why does my terminal go strange when I cat the file?
An ESC character starts an escape sequence, and the terminal obeys it. That is one reason to clean untrusted text before printing it.
Check your own text
Paste anything into the cleaner to see every hidden character it contains, with position, codepoint and what happens to each one. Nothing is uploaded.