macOS

GlazeWM provides a tiling window manager for macOS and Windows, inspired by i3wm.

Audacious plays audio and is described by its project as an open-source player descended from XMMS.

AVPlayer displays and controls up to 16 videos at once, with playlists and keyboard shortcuts for managing playback.

Browse audio plugins, including effects for shaping and processing sound, in the Airwindows collection.

QOwnNotes supports Markdown note-taking on Linux, macOS, and Windows, and works with Nextcloud Notes.

Perspective Grid provides an adjustable perspective drawing grid with vanishing points, spacing controls, zoom, and screenshot export.

Caesium Image Compressor is software for compressing pictures while aiming to preserve visible quality.

Old School RuneScape players can use RuneLite, a free open-source client with downloads for Windows, macOS, and Linux.

View images with qView, a lightweight viewer for Windows, macOS, and Linux with a minimal interface.

MicroPad supports note-taking and note organization, according to its product page.

xbar places output from executable scripts and programs in the macOS menu bar.

Mac Mouse Fix customizes mouse behavior on macOS, according to its product page.

LightPDF provides cloud tools to view, edit, convert, sign, annotate, merge, and manage PDF documents.

Petmate edits Commodore 64 PETSCII images in a cross-platform desktop app that runs locally on macOS, Windows, and Linux.

Notes+ is an iPad note-taking app that supports Apple Pencil and includes learning tools, according to its page.

Hacker Smacker collects writing from supporters and critics of Hacker News in one publication.

Draw and edit pixel art with PyDPainter, a Python-based graphics program.

Learn Python with Thonny, a beginner-focused IDE that includes official installers and programming tools.

adbfs-rootless mounts Android phones on Linux through adb without requiring root access on the phone.

Markpad combines Markdown viewing and editing with a tabbed notepad interface for Windows, macOS, and Linux.

Synfig Studio is free, open source software for 2D animation, with downloads and project information on its site.

Share a terminal in a browser with sshx, which supports multiple collaborators, live cursors, and chat.

Tagaini Jisho is a free, open-source Japanese dictionary and kanji lookup tool for Windows, macOS, and Linux.

Newsboat reads RSS and Atom feeds in a text console and is maintained as a fork of Newsbeuter.