Definition. An on-device document engine converts and renders office files on the same hardware that runs a local model, so the AI feature never has to upload a document to be able to read it. Running a model on the device is a promise to the user that data does not leave; the promise breaks the moment the app must upload a .docx to a conversion service first.
Where is the gap between files and models?
The documents people care about are Office files: a contract in Word, a budget in Excel, a proposal in PowerPoint. Local pipelines usually want something else: page images for a vision model, a PDF for a document pipeline, CSV for a table. Getting from one to the other is a conversion step, and where that step runs decides whether the feature is really on-device.
What can OfficeAPI do beside the model?
OfficeAPI is a Rust document engine that runs fully offline on Windows, Linux, macOS, Android, iOS, and HarmonyOS. Inside your app it can:
- convert Word, Excel, and PowerPoint files to PDF, JPEG/PNG/BMP, SVG/TIFF/EMF, or CSV on the device — 42 documented pairs in total;
- render a preview of the original or generated document in your own UI — 32 documented extensions;
- do both with zero dependencies, so nothing extra is installed next to your model.
Which output should the model get?
| Model input you need | OfficeAPI output | Families |
|---|---|---|
| Page images | JPEG, PNG, BMP | Word, Excel |
| One portable document | Word, Excel, PowerPoint | |
| Tabular data | CSV | Excel |
| Scalable graphics | SVG, TIFF, EMF | Word, Excel |
How do you wire it up?
- Confirm the source extension is a documented conversion input.
- Convert on the device to the format your pipeline reads.
- Hand the result to the model running beside your app.
- Render the source or the generated document with preview so the user can check it.
How do you close the loop with the user?
An on-device AI feature is rarely fire-and-forget. The user wants to see what the model read and check what it produced. Preview handles that: render the source document or the result inside the app, on the same device, without a hosted viewer.
On-device versus cloud conversion
| OfficeAPI on the device | Cloud conversion service | |
|---|---|---|
| Document leaves the device | No | Yes |
| Consistent with an on-device model | Yes | No |
| Works offline | Yes | No |
| Dependencies | None | Client, credentials |
Frequently asked questions
Does OfficeAPI run the model?
No. It converts and previews documents; the model is yours.
Which platforms does this work on?
All 6 supported operating systems: Windows, Linux, macOS, Android, iOS, HarmonyOS.
Is a PDF or an image better for the model?
Use page images (JPEG, PNG, BMP) for a vision model reading Word or Excel pages; use PDF when your pipeline consumes a single document, including PowerPoint.