flangu keeps a full local copy of your decks, cards, review history, and statistics on your device. Anything that reads from that copy works with no connection at all. Anything that has to generate something new from flangu's servers doesn't.
What works offline
- Reviewing. A full review session runs entirely from your device's local copy: cards are drawn from it, and each rating schedules the next review on-device. The review screen makes no network call while you study.
- Browsing your decks and cards, including metadata already attached to a card (definitions, examples, synonyms, pronunciation, and any images already generated).
- Managing decks and cards. Creating, editing, and deleting a deck, and editing or deleting an existing card, all save straight to your device.
- Creating cards manually. The Translator's mode toggle switches to
Manual automatically when you're offline, since Translation mode needs a connection. A manually created card saves the same way any other card does. - Statistics. Every count, chart, and percentage is calculated from your local review history, so your stats screen is exactly as accurate offline as it is online. See How statistics work.
- Audio you've already played. Once a word or sentence's audio has been generated, it's cached on your device and plays instantly with no network call. Anything not yet cached falls back to your device's own speech engine instead of failing. See Audio and text-to-speech.
What needs a connection
| Feature | Why |
|---|---|
| Translation mode | Generates the translation and fills in the back panel using flangu's servers. |
| Linguistic metadata for a new card | Synonyms, definitions, examples, and pronunciation are generated on flangu's servers after the card is created. |
| Vocabulary images | Generated on request from flangu's servers. |
| Personal Tutor | Every message is sent to flangu's servers for a response. |
| High-quality cloud audio | Uses flangu's servers; falls back automatically to your device's built-in speech engine when offline. |
| FSRS optimization | Runs as a background job on flangu's servers. |
| Contact us | Submitting the form needs a connection to reach the flangu team. |
| Manage subscription and Restore purchases | Both talk directly to the App Store or Google Play, not to flangu. |
| Signing in on a new device | Needs one successful first sync before your data appears locally. |
How offline changes catch up
Local writes are saved the moment you make them, independent of syncing. When your connection comes back, flangu syncs automatically the next time the app comes to the foreground, or a short while after you make changes. See Sync now if you want to trigger it immediately instead of waiting.
The one exception is your very first sync after signing in: if that initial pull can't complete, flangu shows a loading screen with a Continue offline option, so you're never stuck waiting on a connection to use the app.
Warning
If you edit the same card offline on two devices before either one syncs, whichever device syncs last overwrites the other's changes entirely. See Editing the same card on two devices.