Adding Custom Compression Plugins to 7-Zip

Official builds of 7-Zip fully support custom compression plugins and external codecs without requiring you to recompile the software or use an unofficial fork. This guide explains how 7-Zip's modular plugin architecture works, which types of plugins are supported, and the exact steps required to integrate third-party compression algorithms—such as Zstandard, Brotli, and LZ4—directly into your standard 7-Zip installation.

Plugin Support in Official 7-Zip Builds

Official releases of 7-Zip are designed with a modular architecture. When the application launches, it automatically scans its installation directory for compatible Dynamic Link Library (.dll) files that implement 7-Zip's native COM-like interfaces (ICompressCoder, ICompressFilter, or archive format interfaces).

This design means you do not need third-party forks to use modern or proprietary algorithms. You simply need the compiled 32-bit or 64-bit plugin files matching your installed 7-Zip architecture.

Codecs vs. Formats

Custom plugins for 7-Zip generally fall into two categories:

  • Codecs: These plugins handle specific compression and decompression algorithms (such as Zstandard, Lizard, or FLAC). They allow standard 7z archives to compress data using non-default methods.
  • Formats: These plugins add support for unpacking or packing specific container formats (such as modern ISO variations, specialized disk images, or game archive formats).

How to Install Custom Plugins

To add custom compression plugins to an official 7-Zip installation, follow these steps:

  1. Obtain Compatible Plugins: Download the plugin .dll files compiled specifically for 7-Zip (popular projects like the 7-Zip ZS plugin suite offer standalone codec binaries). Ensure the plugin architecture matches your 7-Zip installation (x64 for 64-bit, x86 for 32-bit).
  2. Locate the 7-Zip Directory: Open File Explorer and navigate to your main 7-Zip folder, typically located at:
    • 64-bit: C:\Program Files\7-Zip\
    • 32-bit: C:\Program Files (x86)\7-Zip\
  3. Create the Plugin Folders: Check for the existence of two specific subfolders inside the main directory. If they do not exist, create them (administrator privileges may be required):
    • Create a folder named Codecs for compression algorithm libraries (e.g., zstd.dll, brotli.dll).
    • Create a folder named Formats for container format libraries.
  4. Copy the Files: Paste your downloaded .dll files into the appropriate folder (Codecs or Formats).
  5. Verify Installation: Restart 7-Zip. Open the 7-Zip GUI, select a file, and click Add. When configuring the archive parameters with the 7z archive format selected, your newly added compression algorithms will appear in the Compression method drop-down menu.

Important Considerations

  • Architecture Matching: A 64-bit version of 7-Zip cannot load 32-bit plugins, and vice versa. Always match the bitness of the plugin to your installed 7-Zip executable.
  • Compatibility for Recipients: If you compress an archive using a custom codec like Zstandard inside an official 7z container, standard 7-Zip installations without that specific plugin installed will not be able to extract the archive.
  • Security: 7-Zip executes external codecs with the same permission level as the main application. Only install plugins compiled from trusted, verified open-source repositories.