It's probably not completely correct and there's probably issues stemming from the fact that text in web browsers is UTF-16 not UTF-8, but I've used it to quickly figure out that someone's input wasn't being parsed correctly because the spaces were actually non-breaking spaces for example. It can be used for noticing when some text has a letter that looks the same but is actually a different letter than you think (homoglyph attack) or to see what makes up an emoji.
https://verhovs.ky/unicode-debugger/
https://github.com/verhovsky/unicode-debugger
It's probably not completely correct and there's probably issues stemming from the fact that text in web browsers is UTF-16 not UTF-8, but I've used it to quickly figure out that someone's input wasn't being parsed correctly because the spaces were actually non-breaking spaces for example. It can be used for noticing when some text has a letter that looks the same but is actually a different letter than you think (homoglyph attack) or to see what makes up an emoji.