ExtendFS is a read-only ext2, ext3, and ext4 driver for macOS using FSKit. It's plug-and-play, with no kernel extension, external download, or messing with system security settings required. ext4 is one of the most common filesystem formats used by HDDs, SSDs, and USB flash drives formatted on Linux, such as by Ubuntu users. However, ext4 isn't supported by default on macOS and results in an error when you plug one of these devices into your Mac. ExtendFS solves this problem. Enabling the file system extension is easy and only requires you to enable a toggle in System Settings (no rebooting into recovery mode). Once enabled, you can plug in your ext4-formatted drive or open your disk image. Supported volumes will mount automatically, with no command line tools or manual mounting required. Just open the disk in the Finder to access your Linux files. Note that ExtendFS does not support write access to ext2/3/4 volumes and cannot write to files. You can only access files on an existing ext2/3/4 volume created by a Linux computer. Not all ext2/3/4 volumes are currently supported. Please see the "Known Limitations" listed under the website first. ExtendFS is open source with its source code available on GitHub. It is available here on the App Store if you want to support its development.