What Is a .msi File? .msi Format, MIME & How to Open

Quick facts

Extension.msi

File typeWindows Installer Package

MIME typeapplication/octet-stream

CategoryData & Text

Charset—

CompressibleYes

Format familyexe

What is .msi

What is a .msi file?

A .msi file is a Windows Installer Package — Microsoft Installer package for Windows software.

In the mime-db registry it maps to application/octet-stream, and it is marked as compressible. When serving .msi over HTTP, set the Content-Type header as shown in Developer info below.

Related entities: it maps to application/octet-stream — and is delivered over HTTP via the Content-Type header.

How to open .msi files

Use Windows Installer or 7-Zip to open and edit .msi files.
Any text editor (Notepad, VS Code) can inspect the raw content as text.

Developer info

When served over HTTP, responses should set the following header:

Content-Type: application/octet-stream

Common software that reads/writes .msi:

Windows Installer7-Zip

Relation chain

.msiextension of

format

exeserved as

mime type

application/octet-streamsent via header

http header

Related extensions

Related MIME types

application/octet-stream

.bin .dms .lrf

application/x-msdownload

.exe .dll .com

Common uses

Configuration files
Data interchange between systems
API request and response payloads
Logs and data exports

How to edit .msi files

Open the file with Windows Installer, make your changes and save.
Most editors preserve the original formatting and encoding — avoid changing the charset.

How to create .msi files

Create a new file and save it with the .msi extension, or export this format from Windows Installer.

Frequently asked questions

What programs can open .msi files?

Common options include Windows Installer, 7-Zip. You can also open many of these files with built-in viewers or a browser.

How do I create a .msi file?

Create a new file in any text editor or the app that owns the format and save it with the .msi extension.

What is the relationship between .msi and the application/octet-stream MIME type?

application/octet-stream is the media type identifier used for .msi files during network transfer (for example in the HTTP Content-Type header).

Sources & standards

Updated 2026-09-13

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