If you have spent any time in horror-themed forums or creepypasta comment sections, you have probably seen Zalgo text: letters buried under a chaotic stack of marks, as if the words themselves were glitching out. The name comes from an internet meme, "Zalgo," an ominous, unseen entity associated with corrupted, unreadable text that supposedly signals its presence.
Technically, Zalgo text has nothing to do with any actual corruption. It is built entirely from standard Unicode combining characters — the same category of character used for accents like the umlaut in "naïve" or the cedilla in "façade." A font normally expects one or two combining marks stacked on a letter. Zalgo text generators simply add far more than that, often dozens per letter, so they overflow above, below and through the character.
Because the result is plain text rather than an image, it copies, pastes and searches like any other string — it just looks unsettling. That combination of "technically normal, visually chaotic" is exactly why it has stuck around as a favorite for creepy usernames, horror-themed captions and cursed-looking comments for well over a decade.
If you want to try it yourself, the Zalgo generator above lets you control how dense the effect gets, from a light dusting of marks to a full, barely-legible wall of glitch.