EXE Built with PyInstaller Takes Too Long to Open

[07rohanraj]

Hi,

I created an executable using PyInstaller, but I'm experiencing significant delays when opening it. The application should open within 20 seconds, but it is currently taking over a minute.

Here’s some context:

• I used the --onefile and --windowed options in the PyInstaller command.
• The EXE includes multiple imports (like requests, pandas, aiohttp, and others) and assets.

My PyInstaller command:
pyinstaller --onefile --windowed --clean --collect-all nicegui --icon ".\assets\shield.ico" --add-data "assets/*;assets" --add-data "frontend;frontend" --add-data "backend;backend" --add-data "_res/*;cyclonedx/schema/_res" .\backend\SBOM_Generator_GUI.py

[bwoodsend]

There's not really anything we can do about it. Don't use onefile mode. Avoid bloat-heavy libraries like pandas. The rest is between you, your application and Windows.

[07rohanraj]

Okay, instead of onefile i'll go with onedir. Thanks.

[a-sajjad72]

@07rohanraj can you please let the community know, how was the results after using onedir mode. Thanks

[yckonnnnn]

Your command uses --onefile, which explains much of the extra launch time: PyInstaller unpacks the bundled Python modules and support files to a temporary _MEI... folder each time the app starts. Try building the same app as --onedir and compare cold starts; this avoids the one-file extraction step. PyInstaller documents that behavior here: https://pyinstaller.org/en/stable/spec-files.html#adding-data-files.

--clean only clears PyInstaller's build cache; it does not make the built app slower at runtime. If --onedir is still slow, compare the startup time before and after imports, and check whether --collect-all nicegui is including files the app does not need. On Windows, security scanning of a large one-file executable can also add delay. A one-folder build is usually the better fit for a GUI where fast startup matters.