Does “\d” in regex mean a digit?

Question

I found that in 123, \\d matches 1 and 3 but not 2. I was wondering if \\d matches a digit sati

Answer 1

This is just a guess, but I think your editor actually matches every single digit — 1 2 3 — but only odd matches are highlighted, to distinguish it from the case when the whole 123 string is matched.

Most regex consoles highlight contiguous matches with different colors, but due to the plugin settings, terminal limitations or for some other reason, only every other group might be highlighted in your case.