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Overview

Cloud sync uses the Google Drive AppData folder to keep your decks and quiz sessions in sync across devices. The AppData folder is private to the app — it is hidden from the standard Google Drive UI and cannot be accessed by other applications or users. Sync is bidirectional and uses a Smart Merge algorithm that compares updated_at timestamps so the most recently modified version of each deck or session always wins, regardless of which device made the change.

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What gets synced

FileContents
decks.jsonAll decks, cards, statuses, and notes
quiz_sessions.jsonAll in-progress and completed quiz sessions
Image files are stored locally and are not uploaded to Drive. The sync only transfers JSON metadata. When a remote deck is pulled, local image_path values are injected back into the merged deck so image references are never broken.

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Requirements

  • Signed in with a Google account (OAuth)
  • Internet connection (the app detects no-connectivity gracefully)
  • Google Drive API enabled (included in the official build; developers can supply their own credentials.json)

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How to sync

1

Sign in with Google

Open the app and click Sign in with Google. Complete the OAuth consent flow in your browser. Your token is stored in token.json locally and is excluded from Git.
2

Click Sync

Press the Sync button in the desktop app toolbar. This triggers a full sync: decks first, then quiz sessions.
3

Merge runs automatically

The Smart Merge algorithm compares local and remote data and produces a merged result without any user interaction required.
4

Changes are saved and uploaded

The merged result is written to the local JSON files and uploaded back to the Drive AppData folder in a single pass.

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Smart Merge algorithm

The merge logic runs independently for decks and for quiz sessions. The steps below describe deck merging; session merging follows the same pattern.
  1. Download decks.json from Drive AppData
  2. Load decks.json from local storage
  3. For each deck that exists in both remote and local: compare updated_at timestamps — the newer version wins
  4. Decks that exist only on remote are added to the local store
  5. Decks that exist only locally are kept as-is
  6. Save the merged deck list locally (without bumping timestamps)
  7. Upload the merged deck list back to Drive AppData
Timestamp comparison uses ISO 8601 string ordering ("2026-03-15T10:00:00" vs "2026-03-16T09:00:00"). No timezone conversion is performed — all timestamps are generated in local time on the device that made the change.

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Image path preservation

Image files are stored on the local device and are not synced to Drive. When the remote version of a deck is newer and wins the merge, the app re-injects local image_path values for matching cards: 
For each card in the pulled remote deck:
  If a local card with the same card_id has an image_path set:
    → Copy the local image_path into the remote card
This ensures that cards keep their image references even after a remote update overwrites the card data.

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Security

  • Synced files live in the Drive AppData scope — not visible in the standard Drive UI
  • OAuth credentials (credentials.json) and tokens (token.json) are excluded from Git
  • API keys and tokens are masked in the app UI
  • The official build ships with embedded credentials; developers can replace them with their own credentials.json
Never commit credentials.json or token.json to a public repository. These files grant full access to the associated Google account’s AppData.

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Error handling

ConditionBehavior
No internet connectionSync is aborted with message “No network connection”; local data is unchanged
Not signed inSync is aborted with message “Not signed in to Google Drive”
Drive API errorSync reports the HTTP status code (e.g., 403, 500) and stops
Malformed remote JSONRemote data is treated as empty; local data is kept and re-uploaded

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Frequently asked questions

No. The merge only adds or updates decks based on timestamp. A deck present only on one device is never deleted — it is propagated to the other device on the next sync.
Yes. The Android mobile app supports Google Drive sync via expo-auth-session. The same decks.json and quiz_sessions.json files in the AppData folder are used, so changes made on desktop are visible on mobile after syncing.
Go to your Google Account → Security → Third-party apps with account access, find the Flashcard AI app, and remove access. Delete token.json from the app data directory to force a new sign-in.

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Next steps

Study mode

Review your synced decks with keyboard shortcuts.

Export to Quizlet

Export decks to a Quizlet-compatible text file.

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