Unicode code points
The exact identity of every character, including the ones pretending to be others.
What it does
Every character has a number. This shows you that number, so you can tell exactly which character you are dealing with rather than which one it resembles.
Three output formats are available: U+0041 as used in the Unicode standard and most documentation, backslash escape form for pasting into source code, and plain decimal.
Why it matters
Different characters can look identical. Latin a and Cyrillic а are indistinguishable in most fonts and are entirely different characters to any computer. That gap is the basis of homograph attacks, where a domain name or a username looks like one thing and is another.
It is also the fastest way to answer the question of why two strings that appear identical are not equal. Accented characters can be stored either as one combined character or as a letter followed by a separate combining mark, and the two forms compare as different despite rendering the same.
Anything that shows up as a question mark, an empty box or an unexpected symbol becomes diagnosable the moment you can see its actual code point.
Related
Invisible characters finds the characters that render as nothing at all, which this view will then identify precisely.