Quick answer
With notes and highlights kept on your phone, the book itself can work offline when the file is local. Optional online services may not.
The only reliable check is airplane mode.
What should work offline
Opening a local file, moving through pages, saved progress, bookmarks, and local notes should work in a truly offline reader.
What may not work
Cloud sync, online translation, online dictionaries, cover downloads, and new voice downloads can require internet.
If something disappears
Confirm that the file was downloaded, not only cached temporarily by a cloud app.
If the first fix does not work
Try another known-good notes and highlights kept on your phone example. If the second one works, the first file or item is probably the problem. If both fail in the same way, the app, phone, or setting is more likely.
Detailed troubleshooting checklist
Work through the problem in this order: first check notes and highlights kept on your phone itself, then the app, then Android or the device. Keeping that order prevents you from changing many things when only one part is wrong.
- Change one setting at a time.
Test the full flow without a network
For “What works offline with notes and highlights kept on your phone?”, do not stop after seeing the first page offline. Close the app, reopen it without a network, navigate, and resume so you know the whole workflow is local enough for your use case.
- For “What works offline with notes and highlights kept on your phone?”, review the app permissions you actually need and avoid granting unrelated access just to solve a reading problem.
- Download or import the material first, then turn off Wi-Fi and mobile data before testing offline behavior.
- Check which features need a one-time download, such as an optional voice model, before a trip.
What a good result looks like
For “What works offline with notes and highlights kept on your phone?”, offline reading is dependable when the full task still works after a fresh reopen with the network disabled and you know which optional features need internet.
For this guide, stop adjusting once the workflow for “What works offline with notes and highlights kept on your phone?” is clear, repeatable, and easier than the problem you started with.