Sloth

Sloth is a free Mac application that shows you every file, folder, network connection, pipe, and device that any running program on your computer is currently using. If you have ever wondered why a disk won't eject, why an app seems to be accessing files unexpectedly, or which program has a particular port open, Sloth gives you a visual way to find the answer.

Under the hood, it is a graphical wrapper around a built-in Unix command-line tool called lsof, which stands for "list open files." Sloth takes the raw output of that tool and presents it in a sortable, searchable window that is much easier to navigate than a wall of terminal text. You can filter the list by process name, file type, location, or using pattern matching, and you can sort by process name, file count, or other criteria.

The app shows not just regular files and directories but also network sockets (including the port, protocol, and connection status), Unix domain sockets used for communication between programs on the same machine, and pipes that connect one process to another. An inspection panel gives more detailed information about any selected item. A right-click menu provides file operations for items in the list.

Sloth has been in active development since 2004 and is written in Objective-C, Apple's older native Mac programming language. It runs on macOS 11 and later. The current version can be downloaded as a zip file or installed via Homebrew. It is free and open source under the BSD 3-Clause license. The author accepts donations.