How this calculator works
A combining character is drawn on top of the character before it rather than taking a space of its own. Unicode includes a combining low line at U+0332, so placing one after each letter draws a line underneath that letter. The tool adds the mark after every non-whitespace character and skips spaces, tabs and line breaks, which leaves gaps in the line where the words separate. Because the marks are ordinary characters, the underlined text pastes into any field that stores Unicode strings.
Formula
For each character in the input: if it is a space, tab or line break, keep it unchanged; otherwise append the combining low line U+0332. Join the results in the original order.
Worked example
Underline this becomes each visible character followed by U+0332, with the space between the words left bare. The character count output still reports 14 for the original text, because the combining marks do not count as separate visible characters.
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Frequently asked questions
Why is there a gap where the space is?
The tool deliberately leaves whitespace unmarked so the underline breaks between words, which reads more naturally than one continuous line. Some fonts draw a combining mark after a space anyway, but most render the gap.
Can I remove the underline later?
The marks are characters, so deleting them by hand is slow. Keep the original text somewhere and start again if you need plain text, or paste the result into an editor that can strip combining marks.
Does underlined text affect the character count of a post?
It can. Many platforms count the combining marks as characters even though they take no visible width, so a post may hit its limit sooner than the visible text suggests.
Will the line appear in every font?
Combining marks depend on font support. Most modern system fonts draw U+0332, but some older fonts and a few web fonts may show a dotted circle or omit the mark entirely.