Unicode has three kinds of “invisible” characters. Spaces (category Zs) have width and are treated as whitespace. Zero-width format characters (category Cf) have no width and change how text breaks, joins or flows. A third group are blank-looking characters that are formally letters or symbols — such as U+2800 BRAILLE PATTERN BLANK — which is why trimming functions do not remove them.
The boxes in the “Symbol” column show each character between two bars so you can see its width. Use the copy buttons: invisible characters cannot be selected with the mouse. Be aware that many platforms strip or normalize these characters, and that hidden characters in source code or URLs are a known security risk (see bidirectional text for the “Trojan Source” problem).
Click any symbol to copy it. Names link to the full character page with every encoding.