Plenty of places have a ceiling: a meta description around 155 characters, a product title a marketplace cuts off at 80, a database column set to 255, a card preview that shows three lines. When you have a long passage and a short slot, you need to cut cleanly, not just let the platform chop in the middle of a word with whatever it likes.
Set the unit, set the limit, and the shortened text appears on the right.
Characters, words or lines
Characters is the most common and the one with the most subtlety, below. Words is better for summaries and excerpts, since you cannot end up with half a word at all. Lines is for lists, logs and addresses where you want the first few entries.
No half words
With “Do not cut in the middle of a word” ticked, the character cut moves back to the last full word. A limit of 80 might give 76 characters, but it ends on a whole word and any trailing space is removed before the ellipsis goes on. If the first 80 characters contain no space at all, a single long string such as a URL, there is nowhere to step back to and the cut stays as it is.
The ellipsis
The ellipsis is added after the cut and does not count towards the limit. Set the limit three lower if your slot must include it. If you would rather use the single-character ellipsis (…) or no ending at all, change the text in the box. Text that is already short enough is left alone and the stats say so.
What counts as a character
The tool counts Unicode characters, which is not always what a platform counts. Plain letters, digits and most emoji count as one. Family emoji, flags and emoji with skin tones are made of several characters joined together, so they count as more, and a cut that lands inside one could split it. For limits that matter, such as titles and descriptions, finish with the character limit checker, which shows how your text fits a dozen common limits and counts what you see rather than the underlying parts.
Related tools
To clear spaces before measuring, remove extra spaces is worth a pass because spaces count. For a quick total, the word counter. And to fit text into a given width with line breaks rather than cutting it, use the text wrapper.