Genki/WaniKani Kanji Highlighter is a free Chrome extension that helps you apply Kanji that you have learned. It conveniently highlights kanji on the currently viewed webpage based on two learning sources: WaniKani and Genki textbook series.

With this extension, red kanji will be learned in more than 5 levels/chapters, yellow kanji will be learned in 5 levels/chapters or less, and green kanji are already learned. The lighter green corresponds to kanji learned farther in the past. Additionally, grey kanji do not appear in either learning source.

One of the key features of this extension is that it automatically updates your WaniKani level based on your account's API key, which can be found in the WaniKani Settings. The API key is saved to your local browser storage, so you only have to input it once.

If you prefer to use only a single learning source, you can simply disable Genki or choose not to enter an API key.

Overall, Genki/WaniKani Kanji Highlighter is a useful tool for language learners who want to reinforce their Kanji knowledge while browsing the web. It provides a visual cue for the level of familiarity with each kanji, making it easier to recognize and retain the characters.