# Format Fidelity (/guide/format-fidelity)



## High-confidence Preview Lines [#high-confidence-preview-lines]

* PDF, OFD, images, audio, video, Markdown, source code, text, JSON/YAML/TOML/XML/SQL, archives, email, EPUB, Mermaid, Excalidraw, draw\.io, and common Office/OpenDocument files.
* CAD preview is powered by `@flyfish-dev/cad-viewer` through `@file-viewer/renderer-cad`; DWG, DXF, DWF, and DWFx assets stay self-hostable.
* STEP / STP, IGES / IGS, and BREP preview uses a self-hosted OCCT worker, runtime, and WASM module to build renderable meshes locally, with orbit controls, fit-to-view, and unified zoom.
* Word preview uses `@file-viewer/renderer-word` and the self-maintained `@file-viewer/docx` path for readable stream-style DOCX rendering.
* Presentation preview uses `@file-viewer/renderer-presentation` with two isolated native engines: PowerPoint 97–2003 `.ppt` lazy-loads the independently versioned native-WASM `@file-viewer/ppt@0.3.4` runtime, while PPTX/OpenXML lazy-loads `@file-viewer/pptx` and its Worker. Full and CDN/IIFE distributions ship both routes' matching assets; `@file-viewer/ppt` keeps its included license and visible public watermark.

## Structure-first Lines [#structure-first-lines]

Some engineering formats are intentionally conservative:

| Format family | Current behavior                                                                                                                                                                                                              |
| ------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| OLB / DRA     | Safe structure preview for common OrCAD / Allegro containers and readable metadata                                                                                                                                            |
| OAS / OASIS   | Readable fixtures render; complex binary OASIS stays structure-index focused until the dedicated layout kernel matures                                                                                                        |
| IFC           | Optional experimental local visual preview through `@file-viewer/renderer-3d/ifc`, with self-hosted That Open / `web-ifc` assets, fit, selection and property inspection; the official Demo includes IFC4 and IFC4.3 fixtures |
| 3DM           | Signature detection and integration guidance; a dedicated `rhino3dm` renderer is still required for visual preview                                                                                                            |
| PlantUML      | Offline source/SVG-style preview by default; configure an intranet PlantUML service for full server-rendered SVG                                                                                                              |

## Verification [#verification]

Use the built-in checks when the format matrix changes:

```bash
pnpm verify:format-support
pnpm verify:smoke-matrix
pnpm verify:renderer-assets
```