I built a tool that moves your Google Drive files between accounts. Here’s how I made it safe enough to trust.

Description and use

Spillover lets you safely move files between your Google Drive accounts with hash verification, trash‑based undo, and a local transaction ledger.

Problem

The author’s main Google account hit the 15 GB free limit while alternate accounts were empty, requiring a way to rebalance storage across accounts without risking data loss.

Outcome

Spillover enables safe, reversible, and auditable transfer of Google Drive files between a user’s own accounts, preventing accidental data loss and respecting Google’s API limits.

Workflow

• 1. Run spillover run to preview the plan; no files move until --execute is passed and confirmed.
• 2. For each file, download → compute SHA‑256 hash → upload to destination → verify hash matches downloaded bytes.
• 3. If verification succeeds, trash the source file; otherwise log failure and leave source untouched.
• 4. Trashed files remain in the source account’s trash for 30 days, allowing recovery.
• 5. If the process crashes, run spillover resume to continue from the first unfinished transaction stage.
• 6. All moves are recorded in a local SQLite ledger for audit and lookup.

Evidence

spillover run only ever previews the plan. Nothing moves until you pass --execute — and even then it asks for confirmation.

Source

This is the core guarantee: a source file is trashed only after the destination copy’s SHA‑256 hash matches the downloaded bytes.

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Even after verification, originals go to the source account’s trash — not permanent deletion.

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Every file is tracked as a transaction: pending → in_progress → done/failed, with the last completed stage recorded.

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Every move (done, failed, or skipped) lands in a local SQLite ledger: filename, size, hash, source → destination.

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1GB safety buffer per account — a destination is never filled to the brim.

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Since March 2025, Google blocks third‑party apps from reading your full photo library and provides no delete endpoint — so no tool on earth can fully automate Photos moves in 2026.

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