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Renshuu vs Smouldering Durtles: catalog facts
Renshuu	Smouldering Durtles
Freemium Free to start learning, with optional paid features.	Free Free and open source under the Apache 2.0 licence; WaniKani itself is a separate service.
Android, iOS, Web	Android
Vocabulary, kanji and grammar in one place Dictionaries filterable by JLPT level	Native Android interface for WaniKani lessons and reviews Continues a well-known open-source client that was no longer maintained
Japanese only Requires an account to track progress	Only useful with a WaniKani account Android only
Downloadable app, Web application	Downloadable app
Closed source	Open source
License not stated	License: Apache-2.0
Account needed	Account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 24, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.