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Flow vs ッツ Ebook Reader: catalog facts
Flow	ッツ Ebook Reader
Free Free and open source; self-hosting costs only your own server.	Free Free to use, with the source code published on GitHub.
Web, Self-hosted	Web, Self-hosted
Reads EPUB files directly in the browser Docker and docker-compose files for self-hosting	Works with Yomitan and similar dictionary extensions Runs in the browser with nothing to install
Focused on EPUB rather than a wide range of formats Self-hosting requires running a server	Focused on Japanese reading rather than general ebook management Dictionary lookups depend on a separately installed browser extension
Web application, Self-hosted	Web application, Self-hosted
Open source	Open source
License not stated	License not stated
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked October 1, 2026

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