ext4 (fourth extended filesystem) is a journalling file system for Linux, developed as the successor to ext3. Use this tag for question that are ext4 specific, generic file system related questions should use tag [filesystem]
ext4 (fourth extended filesystem) is a journalling file system for Linux, developed as the successor to ext3.
Ext4 information on wikipedia includes hostoric information.
Ext4 is supported on Windows and OSX by commercial software.