Sync your reading position between devices with KOReader

If you read the same book on a Kobo at home and a phone on the train, KOReader’s Progress Sync plugin (often called kosync) resumes each device where the other left off. It is built in — nothing to install.

What it syncs, and what it does not

• It syncs: your position in a document — the page or the exact scroll point.
• It does not sync: bookmarks, highlights, notes, per-book settings, your library, or your fonts. Those stay on each device. If you need highlights in more than one place, that is a different job (a cloud-synced folder of KOReader’s sidecar files, or exporting notes).
• It does not upload your books. The plugin sends a hash that identifies the document, plus a position. No filename, no content, over HTTPS.

Setting it up

The plugin only appears in the menu when a document is open.

1. Open any book. Menu, then the gear, then Progress sync.
2. On the first device choose Register / Login and create an account — a username and password, nothing else.
3. On every other device, open the same menu and Login with that account.
4. Turn on Auto sync so it syncs whenever you open or close a book. There is also a Sync now for a manual push.

KOReader comes with the address of the project’s public sync server already filled in, so for most people steps 1–3 are all there is to it.

The public server versus your own

• The public server is free and run by the KOReader project on a best-effort basis. It works well and is fine for personal use. It can be slow or briefly down, and there is no support if it is.
• Self-hosting is straightforward if you already run a home server: the official sync server is a small service you can start with one Docker command, and several community re-implementations exist. Point every device’s “custom sync server” field at your instance. Worth it if you want reliability or privacy on your own terms; overkill otherwise.

Gotchas

• Both devices must be on the same KOReader account and have opened the book at least once so the hashes match.
• A book that was converted or re-downloaded in between may hash differently and start a fresh position. Keep the same file on both devices.
• Sync is position-only, so if you also want the same bookmarks, put KOReader’s koreader settings/sidecar folder in a synced cloud folder — but only sync when KOReader is closed, or you will get conflicts.

The short version

Open a book, register on one device, log in on the others, turn on Auto sync. The default public server is fine to start; self-host if you want it to be reliable and yours.