Frequently asked questions

useCalibre is a free web service for people who use Calibre. It reads the Calibre library you keep in your own cloud storage (Amazon S3, Cloudflare R2 or any S3-compatible service) and lets you browse, search, read and download your books from any browser, from KOReader and other OPDS reading apps, and offline.

No. useCalibre keeps a copy of your catalog and small covers online, and reads the book files from your storage, so everything works with your computer off. That is the main difference from the Calibre content server.

In your own storage. useCalibre keeps the catalog (titles, authors and similar details), small cover pictures, your reading progress and your settings. Downloads go straight from your storage to you through a link that lasts ten minutes.

Yes. You host your own books, so it costs little to run. It is free with fair-use limits (five Calibre libraries per library, three libraries per person, ten people per library), and readers who find it useful can support it voluntarily.

Amazon S3, Cloudflare R2 and any S3-compatible service, such as Backblaze B2, Wasabi or MinIO. Azure, OneDrive, Dropbox and Google Drive are planned. Until then you can copy a library to an S3-compatible bucket with rclone.

No. A library Calibre manages is read-only to useCalibre: it never writes to it, and it checks metadata.db for damage before importing. Only if you switch a library to “useCalibre manages” does it write, and then it backs up first, keeps anything changed or deleted for 30 days, and keeps Calibre’s metadata.opf for every book so Calibre can take the library back.

Calibre warns against it: sync clients copying metadata.db while Calibre has it open is a common cause of corrupted libraries. The safe setup is to keep the library on your computer and copy it one way to a bucket after closing Calibre. Our cloud guide shows how.

In the browser: EPUB, MOBI, AZW3, AZW, FB2, CBZ and PDF, plus TXT, RTF, DOCX and CBR converted for reading. Every format, including KFX and others, can be downloaded and sent to reading apps.

Yes, through KOReader, which runs on Kobo, Kindle and PocketBook and supports OPDS catalogs: add useCalibre’s catalog once and download books straight to the device. Without KOReader, download a book in the browser and copy it over, or use Amazon’s Send to Kindle.

Yes. On a book’s page, choose Save for offline reading and the book is saved on that device. It opens with no connection, and the pages you read are synced when you are back online. On iPhone and iPad, add useCalibre to the Home Screen first.

No. Books protected with DRM by the store that sold them can only be opened in that store’s app, and useCalibre does not remove DRM. It tells you when a book has DRM instead of showing garbled pages, and you can still download the file.

Yes. Add people as viewers, who can read and download, or editors, who can also add and edit books when useCalibre manages a library. Everyone keeps their own reading progress.

No. useCalibre is an independent service for Calibre users. It is not made by, endorsed by or affiliated with the Calibre project or Kovid Goyal. Calibre is free, open-source software from calibre-ebook.com.

Calibre-Web is excellent self-hosted software, but you run it on your own server and each instance serves one library from local disk. useCalibre is hosted for you, reads libraries from cloud storage you own, merges several libraries into one view, and adds offline reading. Our comparison page covers the details.

Nothing. Your books and your Calibre library stay in your storage, untouched. We promise at least 30 days’ notice before ending the service.

Yes. Switch a library to “useCalibre manages” and upload from your browser. The file goes straight to your own bucket, in Calibre’s folder layout, and useCalibre reads the title, author and cover from the book itself.

Write to the contact address on our privacy policy and we delete your data within 30 days. Disconnecting a library deletes our catalog of it straight away. Your own files are never touched.