Open Source IDE
The editor is where you spend the day, so the costs that matter compound quietly - a vendor that phones home your keystrokes, a format that locks your settings, an extension API that can vanish in a paid tier - long after the syntax highlighting stopped being the point. The open source environments here keep the tool itself open: no telemetry you can't turn off, configuration and plugins in formats you own, and a code base you can extend or fork, so the program you live inside answers to you rather than a roadmap.
Neovim
Vim-based text editor with a built-in API, modern GUIs, and asynchronous job control
Zed
High-performance, multiplayer code editor for macOS, Linux, and Windows
code-server
Run VS Code in the browser on any machine with a consistent development environment
Helix
Modal text editor in Rust with multiple selections, LSP support, and tree-sitter syntax highlighting
Lapce
Rust code editor with built-in LSP, Vim-like modal editing, remote development, and WASI plugins
VSCodium
Free/libre open source binaries of Visual Studio Code with telemetry disabled
Letta
Platform for stateful AI agents with advanced memory, continual learning, and application APIs
Eclipse Theia
Extensible open-source cloud and desktop IDE framework with VS Code extension support
Harper
Offline English grammar and spell checker that runs on your device with WebAssembly support