If you give a wrong answer during reviews, it tries to guess which other WaniKani item you confused it with.
Wanikani Open Framework (https://greasyfork.org/en/scripts/38582-wanikani-open-framework)
Whenever you give a wrong answer during a WaniKani review, the script searches for other WaniKani entries that fit your input, sorts them by visual similarity to the review question, and displays them to the user in a list.
For the visual similarity rating of two kanji it is possible (and recommended) to activate "Use IDS" in the settings menu. This functionality downloads ids.txt (2 MB) from https://github.com/cjkvi/cjkvi-ids which derived this file from CHISE project (http://www.chise.org/).
This script does not send data to servers. Everything is processed locally. The script settings and, if "Use IDS" is activated, the ids.txt are stored as IndexedDB entries in your webbrowser.
For more information about the script see https://community.wanikani.com/t/38432
