Microsoft IIS Compression

IIS Compression is a bundle of two IIS compression scheme providers iisbrotli.dll and iiszlib.dll that enable IIS to compress HTTP response contents. iisbrotli.dll supports Brotli compression, while iiszlib.dll supports both Gzip and Deflate compression.

An IIS compression scheme provider is a pluggable extension of IIS StaticCompressionModule and DynamicCompressionModule - essentially a dynamic link library (dll) that implements the compression algorithm and exposes the IIS HTTP Compression API. IIS StaticCompressionModule and DynamicCompressionModule load the registered compression scheme providers into worker process at runtime, and leverage them to perform compression for static files and dynamically-generated contents, respectively.

Documentation

• IIS Compression Overview
• Using IIS Compression

Installation

Download the Microsoft IIS Compression release from the following locations:

• Microsoft IIS Compression (x86) here.

• Microsoft IIS Compression (x64) here.

The IIS Compression installer registers iisbrotli.dll as the br (Brotli) compression scheme provider in applicationHost.config. It also replaces the default gzip compression scheme provider gzip.dll with iiszlib.dll. A sample httpCompression section in applicationHost.config is shown below:

<httpCompression directory="%SystemDrive%\inetpub\temp\IIS Temporary Compressed Files">
    <scheme name="br" dll="%ProgramFiles%\IIS\IIS Compression\iisbrotli.dll" />
    <scheme name="gzip" dll="%ProgramFiles%\IIS\IIS Compression\iiszlib.dll" />
    <dynamicTypes>
        <add mimeType="text/*" enabled="true" />
        <add mimeType="message/*" enabled="true" />
        <add mimeType="application/x-javascript" enabled="true" />
        <add mimeType="application/javascript" enabled="true" />
        <add mimeType="*/*" enabled="false" />
    </dynamicTypes>
    <staticTypes>
        <add mimeType="text/*" enabled="true" />
        <add mimeType="message/*" enabled="true" />
        <add mimeType="application/javascript" enabled="true" />
        <add mimeType="application/atom+xml" enabled="true" />
        <add mimeType="application/xaml+xml" enabled="true" />
        <add mimeType="image/svg+xml" enabled="true" />
        <add mimeType="*/*" enabled="false" />
    </staticTypes>
</httpCompression>

Build

1. Clone this project with submodules.

git clone --recurse-submodules https://github.com/Microsoft/IIS.Compression.git

2. Build the code using the build.cmd (the location of msbuild.exe needs to be added into PATH environment variable).

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.