If you're looking for a crossword solver that can import puzzles from the web and provide step-by-step explanations, Crossword Genius could be the best option. This AI-based app helps people solve cryptic crosswords by importing puzzles directly from the web. It uses machine vision technology to scan printed crosswords and AI explanations for cryptic clues. It's available for iOS devices and an Android version is coming, and it's good for beginners and experts.
Another choice is NOLEJ, a decentralized AI platform that converts educational content into interactive courseware, including crosswords. You can upload content or enter a URL, and NOLEJ will create interactive quizzes, flashcards and more. That can be useful for creating a range of study materials and assessments, similar to what you might find on Quizlet.
For a more general study aid, Quizlet has a broader learning platform with tools like Magic Notes, Q-Chat and Expert Solutions. It's geared more toward general learning and studying, but it offers millions of solutions and explanations that could be useful for crossword fans looking for other learning materials.