> ## Documentation Index > Fetch the complete documentation index at: https://docs.burakov.net/llms.txt > Use this file to discover all available pages before exploring further. # Deduplication > How Tidybook finds duplicate contacts, why it matches conservatively, and how the review queue plus undo let you merge without fear. Everyone has duplicates and almost nobody cleans them up, because a wrong merge is scary. Tidybook's deduplication is built to **earn your trust first** and save you taps second. ## Conservative matching Tidybook only treats two entries as a **high-confidence** duplicate when they share: * the **same phone number** (compared the way the phone network sees it, not as raw text), or * the **same email address** (case-insensitive). It will **never** merge two contacts just because they share a name. Two different people called "Alex Smith" stay separate — name-only merging is the mistake that loses your data, and Tidybook refuses to make it. ## The review queue Anything that isn't a dead-certain match goes into a **review queue**. For each pair you see what both sides would contribute and choose: * **Merge** — combine them into one contact. * **Keep separate** — they're different people; don't ask again. * **Skip** — decide later. The app does the finding; you keep the final say. ## Merge without losing anything When you merge, Tidybook **unions** the details: every phone, email and address from both cards is kept, and where a single value conflicts it keeps the alternatives available rather than silently picking one. ## Undo any time Every merge is **reversible**. Tidybook remembers the pieces it combined, so you can split a contact back apart later. That safety net is what finally makes it comfortable to tidy a book you've been avoiding for years. Deduplication runs entirely on your device. Even with Sync on, the matching happens locally on your own contacts — the server never sees who your duplicates are.