Underline Text
This underline is not a font setting. It is a single Unicode character, U+0332, inserted after each letter you type, and it is drawn beneath whatever came before it.
These are characters, not formatting, which is why they survive a paste into a bio. It is also why a screen reader will not read them as ordinary letters, and why some sites refuse them in a name field.
The mechanism
The generator leaves your letters alone and puts COMBINING LOW LINE, U+0332, after each. Like the overlay used for strikethrough it is a non-spacing mark: no width, drawn under the preceding character. The spaces are marked too, so the segments meet and read as one unbroken rule.
Where it breaks
- The line sits on the baseline, exactly where the tails of g, j, p, q and y are, and in most fonts it cuts through them.
- Segment ends do not always meet: between a narrow letter and a wide one you can see the seam.
- It is not the underscore key, which is a character of its own that pushes letters apart; this one takes no space.
The practical limits
Each visible character now costs two codepoints, so a 150-character limit holds about 75 underlined ones. Combining marks are also commonly stripped or rewritten by input fields on the way into storage; which fields do that is not predictable from outside, so test yours.
Why underlining is a poor idea
On screen an underline means a link. Underlined text that does nothing when tapped reads as a broken link rather than as emphasis.
Accessibility, plainly
A screen reader has a mark between every pair of letters and commonly announces it, so an underlined word arrives as letters interleaved with descriptions of a line: unusable to a blind visitor. It belongs on a decorative profile line and nowhere else, never in a heading or a name. Nor is it a way past a filter, and stacking marks until glyphs spill onto neighbouring lines is a fault, not an effect. For emphasis that holds together, the alphabets on the fancy text generator hub survive far better, and sans bold is the sturdiest.