> ## Documentation Index
> Fetch the complete documentation index at: https://elephas.app/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# What Syncs and What Stays on Each Computer

> See which Elephas data Personal Sync moves between your computers (Brains, documents, chats) and what stays on each one (search indexes, AI keys, settings).

Personal Sync moves your knowledge: your Brains, your documents and your chat history. Everything that can be rebuilt, or that is personal to one machine, stays on that computer: search indexes, AI keys, app settings and downloaded models.

<Info>
  Personal Sync is part of the Professional plan. See [Personal Sync overview](/docs/sync-and-devices/personal-sync-overview).
</Info>

When you turn Sync on, Elephas puts it in one line: "Brains, documents, and chat history will leave this device as end-to-end encrypted data. Search indexes, AI keys, and app settings stay local."

## Synced, end-to-end encrypted

| What | Details |
| - | - |
| Brains | Name and settings, including your [Protected Names](/docs/brains-and-documents/protected-names) |
| Documents | The original file you added, the text Elephas extracted from it, and its versions |
| Chat history | Your chats, the questions, the answers and their citations, and which Brains each chat used |
| Deletions | Deleting a Brain, document or chat on one computer deletes it on the others |

Only finished results sync. An answer that is still being written does not, and another computer never re-runs a question on its own.

## Stays on each computer

| What | Why |
| - | - |
| Search indexes | Each computer indexes its own copy, on the device. Indexing happens on your computer. Always. |
| API keys for [your own API key](/docs/ai-options/use-your-own-api-key) | Kept in that computer's Keychain or Credential Manager. Add the key on each computer. |
| App settings | Theme, AI choice and other preferences are per computer. |
| Downloaded models | Search, OCR, private-information and [Local AI](/docs/ai-options/run-local-ai) models download on each computer. |
| Device keys | Each computer's private keys never leave it. |
| The database file | Elephas never copies its database between computers. It sends individual encrypted changes instead. |

## How it works

* **Encrypted per Brain.** Each Brain has its own key, and your chats have their own. The sync server stores the encrypted result and cannot read file names, Brain names or chat text. See [Sync encryption](/docs/privacy-and-security/sync-encryption).
* **Text travels with the file.** The text Elephas extracted on the first computer syncs with the file, so every computer works from the same text and the same citations. The receiving computer does not read the file again from scratch.
* **Your Personal workspace only.** Personal Sync covers your Personal workspace. [Team Brains](/docs/teams/team-brains) sync through the Team.
* **Not a backup of your disk.** Sync copies what is inside Elephas. It does not watch or copy the folders your files came from.

### File size

The sync service accepts files up to 512 MB. Elephas currently imports files up to 200 MB, so every file you can add today also syncs.

## Troubleshooting

<AccordionGroup>
  <Accordion title="My AI choice or API key is missing on the other computer">
    That is expected. Settings and keys stay on each computer. Set them up in **Settings › AI** on each one. See [Choose how Elephas answers](/docs/ai-options/choose-how-elephas-answers).
  </Accordion>

  <Accordion title="A synced document isn't searchable yet">
    The receiving computer is still indexing it. The Sync status shows **Indexing synced documents**. If it says the search model is missing, get it back in **Settings › Downloads**, then choose **Sync Now**. See [Sync troubleshooting](/docs/troubleshooting/sync-troubleshooting).
  </Accordion>
</AccordionGroup>

## Related articles

<CardGroup cols={2}>
  <Card title="Personal Sync overview" href="/docs/sync-and-devices/personal-sync-overview" />

  <Card title="Sync encryption" href="/docs/privacy-and-security/sync-encryption" />

  <Card title="Where your data is stored" href="/docs/privacy-and-security/where-your-data-is-stored" />

  <Card title="Sync conflicts" href="/docs/sync-and-devices/sync-conflicts" />
</CardGroup>


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