A combining mark is a character with no width of its own that attaches to whatever precedes it. It is how accents, strikethrough and underline effects are produced in plain text, and how glitch text stacks dozens of marks onto a single letter.
Marks attach backwards
Combining characters modify the character before them. Typing e followed by U+0301 COMBINING ACUTE ACCENT produces é. The mark occupies no horizontal space; the rendering system positions it over the preceding base character. This is why deleting text with combining marks can feel unpredictable — one backspace may remove a mark rather than the visible letter.
Strikethrough and underline in plain text
U+0336 COMBINING LONG STROKE OVERLAY draws a line through its base character, and U+0332 COMBINING LOW LINE draws one beneath. Applying one after every character produces s̶t̶r̶i̶k̶e̶t̶h̶r̶o̶u̶g̶h̶. Because the marks are part of the text, the effect survives pasting into fields with no formatting — which is the entire appeal, and also why it doubles the character count.
How glitch text is built
Zalgo text applies many combining marks to each base character, drawn from the Combining Diacritical Marks block at U+0300 to U+036F. Unicode places no limit on how many can stack, so the marks pile up above and below the line. Rendering engines position them differently, which is why the same string can look quite different on two devices.
The costs are real
Every mark is a character, so a strikethrough phrase is roughly twice its apparent length against any field limit. Heavy stacks overflow their line, overlap neighbouring content and are frequently truncated or stripped by messaging platforms. Text with combining marks does not match a search for the plain word. And a screen reader may attempt to announce each mark, turning a short phrase into a long recitation.
Precomposed versus combining
Many accented letters exist both ways: é is available as the single character U+00E9 and as e plus U+0301. They look identical and are different byte sequences. Normalisation, covered in its own guide, is the process that reconciles them — and the reason a search can fail on text that appears to match exactly.
References
Related tools and guides
Last updated September 2026 · Editorial policy · How we verify Unicode claims