Windows installer MSI format

Question

I cannot find the MSI format specification. It says that its an open standard, but I don\'t see any documentation - just bits and pieces of information here and there.

Answer 1

The binary format is not open, I wouldn't even go as far as calling it a standard.

However I assume it's not the file format you're concerned with (which is undocumented), but rather the tables, actions, sequences, etc. that are visible when interfacing with the MSI via the Windows Installer SDK, API, Orca, etc.

Everything is covered in the SDK documentation, however for some reason search engines don't rank the documentation very highly. Also you can no longer download the Windows Installer SDK separately, it is now bundled as part of the Windows SDK.

• Windows Installer SDK Documentation
• Windows SDK Download

Answer 2

Microsoft has published the MSI file format details. You can download the specifications for the various versions here: [MS-CFB]: Compound File Binary File Format

The latest version at the time of this writing is 9.0, released on 9/12/2018. You can download it as a PDF here.