OmniView

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A Windows file viewer built around one fairly ordinary annoyance: there is always some file on your machine — a PDF, a DOCX, an Excel sheet, a PSD, an archive, a video — and opening it means installing yet another suite of software first.

OmniView is my attempt to make that part simpler. One native window, a small core, and optional plugins for the formats that need more than the core can reasonably carry.

It is not a replacement for Office, Photoshop, or AutoCAD. It is a viewer: open the file, look at it, check the contents, move on. For real editing, use the tool that is actually good at editing.

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Download and install

The latest build is on the Releases page.

Download OmniView-Setup.exe and run it. It extracts the core to:

%LOCALAPPDATA%\OmniView\0.3

and starts the app.

The first launch asks you to pick an interface language. Your files are always displayed in their original language; only the UI is translated.

The core alone is enough for many people

The core handles PDF, plain text, code, images, audio/video, archives, and SQLite. If that is all you need, you can stop here.

Add plugins only when you need them

The release also contains separate .ovp packages:

office.ovp   DOCX / XLSX / PPTX / ODT / ODP / RTF
ebook.ovp    EPUB / MOBI / AZW3
data.ovp     Access / DBF / HDF5 / ONNX / PT / PKL / TFLite / mail stores
pro.ovp      STL / OBJ / GLB / DXF / SHP / KML / GPX / EXE / ELF / fonts
raw.ovp      PSD / AI / camera RAW
hello.ovp    a small example of a user-made plugin

The easiest path is to double-click Install-All-Plugins.cmd. It closes any running OmniView instance, installs the plugins next to it into:

%LOCALAPPDATA%\OmniView\plugins\

and starts OmniView again.

You can also install one plugin at a time:

• Open a file that needs it and click Install from .ovp file…
• Or open Help → Plugin Manager… → Install .ovp…
• Or drag an .ovp file into the OmniView window

A few practical notes:

• Installing/updating closes the running OmniView. Save any edited text first.
• The build is not code-signed, so Windows SmartScreen may say “Unknown publisher”. Use More info → Run anyway.
• Do not install plugins you do not need.

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What it can do

The core does not rely on Office, WPS, Photoshop, AutoCAD, 7-Zip, or FFmpeg being installed on the machine.

• PDF: native PDFium rendering, page navigation, zoom, fit-to-width
• Text/code: encoding detection, syntax highlighting, editing for ordinary text files
• Images: PNG, JPEG, GIF, WebP, TIFF, BMP, ICO, SVG, and more
• Audio/video: decoding through Qt's bundled FFmpeg
• Archives: ZIP, 7Z, RAR, TAR, ISO, and others via a bundled 7-Zip
• SQLite: open a database and inspect tables and rows

Plugins add:

• Office documents: DOCX, ODT, RTF, XLSX, PPTX, ODP
• E-books: EPUB, MOBI, AZW3
• Data and models: Access, DBF, HDF5, ONNX, PT, PKL, TFLite
• 3D/CAD/GIS: STL, OBJ, GLB, DXF, SHP, KML, GPX
• RAW/PSD: camera RAW, Photoshop PSD, AI

The honest part:

• DOCX and PPTX are reflowed natively. They are not pixel-identical to Word or PowerPoint page layout.
• DWG currently exposes headers, version, and embedded strings. DXF is rendered properly.
• STEP, BLEND, SKP, and PST are structural/metadata views, not full professional kernels.
• Video seeking depends on the file's index. A damaged or index-less stream may only play sequentially.

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Why not one giant .exe?

The first version was a 105 MB single executable with everything inside.

It worked, but it had two problems:

1. every user paid the size cost for formats they never opened;
2. changing one dependency meant shipping the whole thing again.

The current version is split into three layers:

• Core: native window, PDF, text, images, audio/video, archives, SQLite
• Plugins: Office, e-books, data, 3D, RAW — independent packages
• Setup: a self-extracting launcher that unpacks the core on first run

The extracted core is about 186 MB; the setup is about 62 MB. Plugins range from roughly 1 MB to 25 MB, and you only install the ones you want.

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Large files

This is where most of the engineering time went.

Text

Text files over 8 MB are no longer loaded into the editor as one string. OmniView uses mmap and decodes a window of roughly 2 MB at a time.

Previous/next chunk and percentage jumps are available. Only the current window lives in the editor.

A 30 MB log may hold 1–2 MB of characters in the widget; a 500 MB file does not become one giant Python string.

Spreadsheets

A normal .xlsx goes through openpyxl. If the file is over 8 MB, or the active sheet has more than 20,000 rows, OmniView switches to a streaming viewer instead.

The streaming path reads the worksheet XML in row windows (300 rows at a time), keeps shared strings in a disk-backed SQLite index, and never builds a QTableWidgetItem for the whole workbook. It shows values, not the full cell styling.

Jumping to a distant row still has to scan from the start of the sheet XML. It is slower than a normal workbook, but it should not consume gigabytes of RAM.

Video

Playback uses Qt's QMediaPlayer as a stream. Nothing is transcoded and the whole video is not cached in memory.

Whether a very long video seeks well depends on the container and its index, not just the duration. A damaged stream without an index can only play in order.

PDF

Only pages near the current viewport are rendered. The whole document is not rasterized on open.

Archives

The listing comes from 7-Zip; an entry is extracted to cache only when you open it.

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Languages

The first launch asks which interface language you want.

The list includes the six UN official languages plus languages with more than 30 million speakers — 58 entries in total.

The translation status is uneven, and I would rather say so:

• Complete catalogs: en / zh / fr / es / ru / ar
• The rest currently fall back to English and are marked English fallback in the picker

Catalogs are plain JSON:

omniview/locales/<code>.json

You can contribute through a PR, or drop a file into:

%LOCALAPPDATA%\OmniView\locales\<code>.json

Only the interface is translated. File contents are never translated.

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Plugins and making your own

An .ovp is just a zip:

myplugin.ovp
  plugin.json
  plugin.py          # optional custom viewer
  site-packages/     # optional dependencies

plugin.json:

{
  "id": "hello",
  "name": "Hello Viewer",
  "version": "1.0.0",
  "formats": ["hello"],
  "entry": "plugin.py",
  "factory": "create_viewer"
}

plugin.py returns a ViewerBase:

from omniview.ui.common import ViewerBase


class HelloViewer(ViewerBase):
    ...


def create_viewer(path, parent=None):
    return HelloViewer(path, parent)

A working template is in the repo:

python build_ovp.py --template plugins/hello
python build_ovp.py --source plugins/hello --out plugins/hello.ovp

Install hello.ovp, then open a .hello file to see it in action.

The full format reference is in docs/PLUGIN_FORMAT.md.

When parsing fails

OmniView does not exit silently, and it does not just show a modal and forget about it.

It opens a red Unable to parse this file tab with:

• the file path
• the plugin id
• the full traceback
• Copy error
• Open Plugin Manager
• Open file location

If the plugin is missing, you get a separate page with the plugin size, an install button, and Install from .ovp file….

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Run from source

pip install -r requirements.txt
python app.py

The core does not need the plugin dependencies.

Build the full release

pip install -r requirements.txt -r plugin_requirements.txt -r dev-requirements.txt

python build_office_plugin.py
python build_plugins.py
.\build_core.ps1
.\build_setup.ps1

Output:

release\OmniView-Setup.exe
plugins\*.ovp

Building the setup requires 7-Zip on the machine, or:

$env:SEVENZIP = "C:\path\to\7z.exe"

Pushing a v* tag lets GitHub Actions build and publish the release.

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Uninstall

Run packaging\Uninstall.cmd, or delete:

%LOCALAPPDATA%\OmniView\0.3

Plugins are kept by default in:

%LOCALAPPDATA%\OmniView\plugins

Delete that directory too if you want a clean removal.

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Known limitations

• DOCX/PPTX will not match Office page-for-page.
• DWG is still a metadata view; full DWG needs a LibreDWG plugin.
• STEP/BLEND/SKP/PST are structural views.
• Video seek depends on the file index.
• Very large text is read-only chunked mode; it does not edit the original file in place.
• Plugins are not signed or sandboxed. .ovp files execute Python code; only install ones you trust.
• Plugin checksums, delta updates, and crash reporting are still on the list.

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License

• Core and original plugin code: FSL-1.1-ALv2, converting to Apache-2.0 after two years. Full text in LICENSE.
• ebook.ovp contains GPL-3.0 mobi/KindleUnpack and GPL-2.0 unidecode; the plugin package as a whole is distributed under GPL-3.0-compatible terms.
• data.ovp contains GPL-3.0 extract-msg and RTFDE; the plugin package as a whole is distributed under GPL-3.0-compatible terms.
• office.ovp, pro.ovp, and raw.ovp use mostly MIT/BSD/Apache dependencies. Qt/PySide6 is LGPLv3; 7-Zip is LGPL.
• Full third-party notices and bundled plugin licenses: THIRD_PARTY_NOTICES.md.

The FSL core and the GPL plugins are separate components. Do not describe the whole release as FSL or MIT.