Best compression settings in Inno Setup compiler

Question

What are the best settings for the smallest file size output?

That can equal or surpass this setting in FreArc

Answer 1

For the best compression use:

[Setup]
SolidCompression=yes
Compression=lzma2/ultra64
LZMAUseSeparateProcess=yes
LZMADictionarySize=1048576
LZMANumFastBytes=273

• Use defaults for other compression-related directives.
• Run the compiler on x64 system.
• With the SolidCompression, it helps, if you order files in the [Files] section by an extension and similarity. Though the solid compression is not recommended for huge installs.
• You can use LZMANumBlockThreads to speed up the compression.

With this settings, you will need up to 11 GB of memory on the machine that runs the compiler; and up to 1 GB of memory on the system that runs the installer.

For details, refer to the Compression directive documentation.

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Though I'm not sure, if you can match FreeArc even with this settings.

If you want to use FreeArc compression, use unarc.dll.

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Note that ISTools does not allow the lzma2, as that was introduced in the Inno Setup 5.3.9. Always use the latest version of Inno Setup.