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

# File preview

> Server-side rendering of docx, xlsx, pdf, pptx, images, and code — inline in the chat.

<Frame>
  <img src="https://mintcdn.com/yambr/AQ23_2YQrfJDjXh_/images/screenshots/02-file-preview.png?fit=max&auto=format&n=AQ23_2YQrfJDjXh_&q=85&s=4a4d18ab8e2ef79562e5c49cfd02c9ff" alt="File preview panel showing a generated .docx cover letter" width="1748" height="1646" data-path="images/screenshots/02-file-preview.png" />
</Frame>

## What the user sees

When the model creates a file, a link appears in the chat. For any renderable file type, a preview iframe auto-inserts right after the link:

| Type                     | How it renders         |
| ------------------------ | ---------------------- |
| `.docx`                  | Mammoth → HTML         |
| `.xlsx`                  | Multi-sheet table view |
| `.pdf`                   | Page-by-page canvas    |
| `.pptx`                  | Slide navigation       |
| `.md` / `.mdx`           | Markdown preview       |
| `.html`                  | Inline iframe          |
| `.png` / `.jpg` / `.svg` | Direct                 |
| Source code              | Syntax-highlighted     |

All rendering happens server-side. The browser only loads an iframe — no client-side PDF.js, no heavy dependency trees.

## URL shape

Files live under `/files/{chat_id}/{relative/path}` on the Computer Use Server:

* Managed: `https://cu.yambr.com/files/{chat_id}/...`
* Self-hosted: `http://localhost:8081/files/{chat_id}/...`

Previews are served from `/preview/{chat_id}/{path}` (same host). See [cu.yambr.com](/platform/cu-endpoint) for security implications.

## How the iframe auto-inserts

The Open WebUI filter's `outlet()` finds links of the form `{PUBLIC_BASE_URL}/(files|preview)/...` in assistant messages. On the patched Open WebUI image, the `fix_preview_url_detection` frontend patch sees those links and promotes them to a synthetic `<iframe>` artifact; `fix_artifacts_auto_show` then opens the side panel. On stock Open WebUI, the link stays a link — still works, just without the auto-open. Full mechanics: [Open WebUI filter](/integrations/open-webui-filter).

## Archive download

Every message that references at least one file gets a **Download all files as archive** button. It hits `/files/{chat_id}/archive` on the server and streams a zip of every output the sandbox has written for that chat.

## Uploads

Drag a file into the chat input. It lands at `/data/uploads/{chat_id}/{filename}` on the host and is mounted read-only at `/mnt/user-data/uploads` inside the sandbox. The model sees it as an MCP resource (`resources/list`) and via the system prompt.

## Why files stay on the server

* **No chat size limit** — files never flow back through message context.
* **Direct access** — open any file URL in a new tab.
* **One zip download** for the whole session.
* **No re-upload** — the client doesn't store files locally.

## Related

* [cu.yambr.com](/platform/cu-endpoint) — public file URLs on managed Yambr
* [Open WebUI filter](/integrations/open-webui-filter) — how the preview auto-insert works