This is AWESOME for Japanese learners. There are 46 basic hiragana that represent the sounds of Japanese but many thousands of Kanji, and it’s incredibly hard to read Japanese even if you’ve been studying for years.

A few people here rightly pointing out inaccuracies and other methods of display (ie Ruby tags) but IMO they are somewhat missing the usefulness here - there are many applications (ie e-readers, random web contexts, custom apps etc) where the traditional methods of display are hard or fail. I recently ran into it trying to get custom Japanese ebooks to display furigana with ruby tags on my kindle. It’s a giant nightmare. Excited to try this out.