dan

A fast, modeless, lightweight terminal text editor written in Rust. Designed for zero-configuration deployment, dan maintains ultra-low input latency even over high-jitter SSH connections and delivers high-performance operations on massive files thanks to its Rope buffer architecture.

Key performance metrics:

• Memory footprint: Typically consumes < 20MB RSS.
• File handling capacity: Fluid, non-blocking navigation and manipulation of 100MB+ log files.
• Bandwidth optimization: Implements aggressive rendering optimizations to minimize transmitted escape sequences.

Architectural comparison

Feature	Dan	Vim	Nano	Micro
Modeless	✅	❌	✅	✅
Rust-based	✅	❌	❌	✅
Atomic Saves	✅ (fsync/rename)	⚠️ (Configurable)	❌	❌
Buffer Architecture	Rope $O(\log N)$	Gap buffer/Piece table	Flat string	Gap buffer
Rendering	Differential	Full/partial redraw	Full redraw	Full redraw
Crash Recovery	✅ Auto-swap	✅ Swap files	❌	❌
Command Palette	✅	❌ (Cmd line)	❌	❌
Out-of-box Config	Zero-config	High learning curve	Minimal	Minimal

Quick install

Install or update Rust:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Clone, build, and install Dan:

git clone https://github.com/dfallman/dan.git
cd dan
cargo install --path .

For more installation options, see Installation.

Features

Dan uses familiar shortcuts out of the box — Ctrl-C/V to copy/paste, Ctrl-S to save, Ctrl-Z/Y to undo/redo, Ctrl-Q to quit. Press Ctrl-H to toggle the built-in help bar at any time.

• Rope-Backed Text Buffer: Utilizes a rope structure ensuring $O(\log N)$ time complexity for insertions and deletions. Memory usage scales with edit volume rather than raw file size, permitting fluid, non-blocking navigation and manipulation of 100MB+ log files.
• Optimized Terminal I/O & Differential Rendering: Implements differential rendering to minimize bandwidth by emitting ANSI escape sequences strictly for modified cells. To sustain $O(1)$ scroll performance in massive files, dan maintains a syntax snapshot cache every 200 lines, eliminating the need to re-lex the entire visible range during rapid vertical movement.
• POSIX-Compliant Atomic Writes (Crash-Safe I/O): File writes are executed via a temporary sibling file, followed by an fsync and atomic rename. A system crash or disk-full condition mid-save leaves the original file intact, preserving original file permissions and symlink targets.
• Crash Recovery: Periodically checkpoints the active buffer to a hidden .swp file every 5 seconds using safe write patterns. Unplanned terminal disconnects or crashed sessions trigger automatic recovery prompts on the next open.
• Interactive Command Palette (Ctrl-P): A fuzzy-search overlay covering all editor actions, active buffers, and project workspace files to keep operations entirely on the home row.
• Multiple Buffers: Concurrent support for multiple active buffers, indexed and managed via the command palette.
• Context-Aware Syntax Highlighting: Powered by syntect with broad language grammar support. Queries the terminal background at startup to apply adaptive themes (OneHalfDark/OneHalfLight) automatically, with immediate toggling via Ctrl-T.
• Background Auto-Formatter (Ctrl-L): Pipes buffer contents to external formatters (Prettier, Rustfmt, Ruff) on a background thread. Formatted output is applied transactionally only if the buffer was not modified during execution.
• Fuzzy Search & Destructive Replace: Instant buffer-wide searching with Ctrl-F, easily promoted to standard find-and-replace using Ctrl-R.
• Unicode & CJK Support: Correct visual alignment, cell measurements, and cursor positioning for double-width characters and complex emoji.
• Native Clipboard Integration: Cross-platform clipboard access using arboard, falling back gracefully to an internal in-memory buffer on headless SSH sessions without display servers.
• Auto-Pairs & Wrap-on-Type: Automated closure insertion for brackets and quotes, with contextual wrap behavior when keys are typed over an active selection.
• Robust Encoding Detection: Scans and parses legacy encodings (Shift-JIS, Windows-1252, etc.) utilizing Byte Order Mark (BOM) sniffing, normalizes to UTF-8 internally, and transparently round-trips to the native encoding on save.
• Active Content Sanitization: Sanitizes raw terminal escape sequences at render time. Malicious or hostile files containing raw ANSI codes cannot alter terminal chrome or exfiltrate local clipboard states.
• Hierarchical Configuration: Evaluates settings through a layered model: core defaults → ~/.config/dan/config.toml → local workspace .editorconfig rules.

Keyboard shortcuts

Basic operation

Key	Action
↑ ↓ ← →	Move cursor
Ctrl + S	Save
Ctrl + A	Save As
Ctrl + Q	Quit (prompts if there are unsaved changes)
Ctrl + H	Toggle help bar
Ctrl + P	Command palette (actions, buffers, project files)

Text editing

Key	Action
Ctrl + C / X / V	Copy / Cut / Paste
Ctrl + Z / Y	Undo / Redo
Ctrl + D	Duplicate line or selection
Ctrl + K	Delete line or selection
Ctrl + E (or Ctrl + /)	Toggle comment (syntax-aware)
Ctrl + T	Toggle syntax highlighting
Ctrl + W	Toggle word wrap
Ctrl + R	Toggle whitespace markers
Ctrl + L	Format document
Alt + ↑ / ↓	Move line up / down
Tab / Shift + Tab	Indent / Dedent

Selection

Key	Action
Ctrl + \	Select all
Shift + Arrows	Extend selection
Ctrl/Alt + Shift + ← / →	Extend selection by word

Navigation

Key	Action
Ctrl + ↑ / ↓	Scroll without moving cursor
Ctrl + Shift + ↑ / ↓	Fast scroll
Ctrl / Alt + ← / →	Jump by word
Ctrl + Home / End	Jump to start / end of file
Ctrl + G	Go to line

Search & replace

Key	Action
Ctrl + F	Search
Ctrl + R (while searching)	Promote to find-and-replace

Note for macOS users: Terminal emulators use escape sequences dating back to the late 70s and some at the time highly influential video display terminals such as VT100. Long story short, this means some "modern" key combinations available in GUI editors can't be distinguished in a terminal. Most notably, Dan (and other terminal apps) uses Ctrl where a Mac user might expect ⌘. Many terminal emulators (including iTerm2) let you remap ⌘ to Ctrl if you prefer, although it can create side-issues. Additionally, the built-in Terminal.app is not recommended: a third-party emulator such as iTerm2, Kitty, Ghostty, or WezTerm will give better results.

Installation

Dan requires Rust v1.94 or later. We recommend installing via rustup rather than your system package manager, which often provides an older version:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

To install on Windows, follow these instructions.

macOS & Linux

git clone https://github.com/dfallman/dan.git
cd dan
cargo build --release
cp target/release/dan /usr/local/bin/
# or
<img width="2180" height="1806" alt="CleanShot 2026-06-04 at 15 12 03@2x" src="https://github.com/user-attachments/assets/3bf61843-f315-4cce-8bdc-c4bea84352c2" />

Windows

Note: If you're running Dan inside WSL, follow the Linux instructions above instead.

git clone https://github.com/dfallman/dan.git
cd dan
cargo build --release
Copy-Item target\release\dan.exe ~/.cargo/bin/

Configuration

Dan works without any configuration file. To customize it, create ~/.config/dan/config.toml (on Windows: C:\Users\<username>\AppData\Roaming\dan\config.toml) and add the options you want to change. Full defaults are shown below for reference.

dan ~/.config/dan/config.toml

# Display
wrap_lines = true           # Wrap long lines (default: true)
tab_width = 4               # Visual tab width (default: 4)
expand_tab = false          # Insert spaces instead of tabs (default: false)
line_numbers = true         # Show line numbers (default: true)
highlight_active = true     # Highlight the current line (default: true)
scroll_off = 5              # Lines to keep visible above/below cursor (default: 5)
fast_scroll_steps = 10      # Lines jumped per fast-scroll keypress (default: 10)
show_full_path = false      # Show full file path in toolbar (default: false)

# Editing
auto_indent = true          # Match indentation of the previous line (default: true)
auto_close = true           # Auto-insert closing brackets and quotes (default: true)
syntax_highlight = true     # Enable syntax highlighting (default: true)

# Interface
show_help = true            # Show shortcut bar at the bottom (default: true)
show_encoding = true        # Show file encoding in status bar (default: true)
show_lang = true            # Show detected language in status bar (default: true)

# Theme
theme = "default"           # Syntax highlight theme; "default" auto-detects terminal background
comments_are_italics = true # Render comments in italics (default: true)

Project-aware settings

Dan automatically picks up .editorconfig files in the project tree. Tab width, line endings, and trailing-whitespace rules defined there take precedence over your global config, so Dan adapts to each project's style without manual adjustment.

Themes

When theme = "default", Dan queries your terminal's background color at startup and picks OneHalfDark for dark terminals or OneHalfLight for light terminals. Toggle syntax highlighting on/off at any time with Ctrl-T.

To use a specific theme, set it in your config:

theme = "DarkNeon"

Note: macOS's built-in Terminal.app does not render ANSI colors correctly. A third-party terminal emulator is recommended for best results.

Available themes:

Theme	Style
OneHalfDark	Clean modern dark (default for dark terminals)
OneHalfLight	Clean modern light (default for light terminals)
Dracula	High-contrast dark, purple/pink accents
Nord	Arctic-inspired dark
Monokai Extended	Classic Monokai, updated
Monokai Extended Bright	Higher-contrast Monokai variant
Monokai Extended Light	Light-background Monokai
Monokai Extended Origin	Original unaltered Monokai
Visual Studio Dark+	VS Code default dark
GitHub	Light, mimics GitHub's code view
Solarized (dark) / Solarized (light)	Classic low-contrast Solarized
gruvbox-dark / gruvbox-light	Warm, earthy retro tones
Coldark-Cold	Blue-tinted light
Coldark-Dark	Cool-blue dark
DarkNeon	Vibrant dark with neon accents
Sublime Snazzy	Bright, elegant dark
TwoDark	Atom One Dark with slightly better contrast
1337	High-contrast dark
zenburn	Low-contrast, easy on the eyes
base16 / base16-256	Standard base16 (256-color variant available)
ansi	Uses your terminal's 16 built-in ANSI colors

Formatter

Ctrl-L pipes the current buffer to an external formatter in a background thread. The formatted result is applied only if the buffer hasn't changed during formatting — keystrokes made while a slow format runs are not discarded. Dan detects the right formatter based on file type:

• Rust: rustfmt — rustup component add rustfmt
• Python: ruff — pip install ruff
• JS / TS / JSON / CSS / HTML: prettier — npm i -g prettier

Formatter output and errors are shown in the status bar.

Note on AI use

I've been writing code for over 30 years. Lately, LLM agent-enhanced coding practices have rekindled my sense of awe at what's possible. This project has been built using a range of tools. By leveraging advanced LLMs for boilerplate generation, rapid prototyping, and automated unit testing, development efforts were focused on high-level architectural decisions, robust edge-case verification, and low-level performance optimizations.

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License: GNU General Public License v3.0 (GPLv3)