How does zalgo text actually work?

Zalgo text works by attaching multiple Unicode combining marks to each character — special code points that render on top of the character before them instead of taking their own space, and can be stacked without limit.

Unicode defines "combining characters" for cases like accents — the é in café is really e plus a combining acute accent, or a single precomposed character, depending on encoding. Ordinary text uses at most one or two combining marks per letter.

Zalgo/glitch generators exploit the fact that nothing in the Unicode standard actually limits how many combining marks you can stack on one base character. Add enough of them — above the letter, through it, and below it — and the letter becomes visually buried under the marks, reading as corrupted or "glitched."

See the full list of marks this site uses in the Unicode combining characters glossary entry, or generate your own with independent control over each zone on the glitch font generator.