LiteDiff

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A local text and code diff tool

Pure-Rust diff engine · Native Tauri v2 window · No Electron

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Download

Get installers from Releases. Each release includes:

Platform	File	Notes
macOS (Apple Silicon)	LiteDiff-*-macos-arm64.dmg	Open and drag to Applications
macOS (Intel)	LiteDiff-*-macos-x64.dmg	Same as above
Windows 10/11 (x64)	LiteDiff-*-windows-x64.exe	Installer; no administrator rights required
Windows portable	LiteDiff-*-windows-x64.zip	Extract and run; no installation needed

Installation notes:

• macOS -- the build is ad-hoc signed but not notarized (notarization requires a paid Apple Developer account). If the first launch is blocked as an unverified app, open System Settings -> Privacy & Security -> Open Anyway, or run:

  xattr -dr com.apple.quarantine /Applications/LiteDiff.app

• Windows -- run the .exe. It installs for the current user and does not trigger a UAC prompt. If WebView2 is missing, the installer downloads it automatically.

Verify your download: every release includes SHA256SUMS.txt.

shasum -a 256 -c SHA256SUMS.txt    # macOS
certutil -hashfile <file> SHA256  # Windows

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Features

Diff engine (pure Rust, no third-party runtime dependencies)

• Linear-space Myers with middle-snake and common prefix/suffix trimming; peak memory is O(N+M), and optimality is validated against a DP LCS oracle
• Word-level inline highlighting: foo_bar -> foo_baz highlights only bar/baz instead of splitting every character
• Ignore leading/trailing whitespace, all whitespace, or letter case; CRLF and LF are treated as equivalent

Interface

• Seven UI languages: Simplified Chinese, English, Traditional Chinese, Japanese, Spanish, German, and French; can follow the system language
• Side-by-side split view <-> unified inline view
• Fixed-row-height virtual scrolling; a 3,000+ line file renders only about 20-40 rows around the viewport
• Strict vertical and horizontal scroll synchronization between panes
• Automatic collapse of long unchanged regions, with per-region expand/collapse and expand/collapse-all controls
• Collapsed regions show the hidden line-number range; line-number width adapts to the file size
• Canvas-rendered minimap with click, drag, and keyboard navigation
• Three levels of change emphasis: row background, 3 px gutter marker, and word-level highlight

Interaction

• Paste directly into either side of the start screen (Cmd+V), or drop a file onto one side
• Cmd+N or the re-enter action returns to the paste screen
• Cmd+S performs an atomic write to disk
• Dark, light, and system themes
• Settings panel (Cmd+,): accent color, red/green color-blind mode, highlight intensity, font size and line height, line numbers and minimap toggles, collapse threshold, leading/trailing whitespace, and case sensitivity

Git history

• Open any local repository and filter files by path
• Compare the working tree against any revision, or compare two revisions
• Historical revisions are always read-only. When comparing one against the working tree, Cmd+S can save only the working-tree file that holds a valid backend capability
• Git reads disable repository hooks, fsmonitor, external diff, signature display, and unnecessary global configuration
• Local branch switching is restricted: dirty worktrees are refused rather than forced, and repository content filters are not allowed to execute

Comparison history

• Every comparison is stored locally and can be restored as a tab after reopening the app
• Grouped by day (Today / Yesterday / date), with per-item delete and clear-all actions
• Retention can be configured in Settings by days or by item count; 0 means unlimited
• Data stays in the local app-data directory and is never uploaded; comparisons larger than 4 MB are not recorded because truncating them would create a different diff

Keyboard Shortcuts

Shortcut	Action
⌘] / ⌘[	Next / previous change
⌘D	Toggle split / inline view
⌘⇧W	Ignore leading/trailing whitespace and line endings
⌘⌥E	Expand / collapse all unchanged regions
⌘F	Find in the current comparison
⌘S	Save
⌘T / ⌘N	New tab (return to paste screen while keeping existing comparisons)
⌘W	Close current tab
⌘,	Open / close Settings
⌘G	Open / close Git history
⌘Y	Open / close comparison history

Build from Source

Requires Rust 1.75+ and Node 18+.

# Dependencies
cd app && npm ci && cd ..

# Tests
cargo test                # Rust
cd app && npm test        # Frontend

# Package for macOS: produces .app and .dmg
./scripts/package-macos.sh
SKIP_DMG=1 ./scripts/package-macos.sh   # .app only; faster for local iteration

# Package for Windows: produces an NSIS installer and portable zip (run on Windows)
powershell -ExecutionPolicy Bypass -File scripts\package-windows.ps1

Releases are built by .github/workflows/release.yml. Pushing a v* tag builds on macOS (arm64 and x64) and Windows, attaches the artifacts and SHA256SUMS.txt to a draft release, and waits for manual confirmation before publishing.

For development, run the app in two terminals: cd app && npm run dev and cargo run -p litediff-app.

Development Workflow

LiteDiff uses a lightweight, repository-native Spec-Driven Development workflow. Before changing behavior, read:

• CONTRIBUTING.md for setup, change levels, tests, and PR expectations
• docs/sdd/workflow.md for the L0-L3 process
• specs/product/litediff.md for the current product and safety baseline
• AGENTS.md for the repository-wide automation rules

Run the full quality gate with bash scripts/verify.sh on macOS/Linux/Git Bash, or powershell -ExecutionPolicy Bypass -File scripts\verify.ps1 on Windows.

System Requirements

• macOS 11+ (Big Sur or later), with native builds for both Apple Silicon and Intel; installers are about 2.3 MB
• Windows 10 / 11 (x64) with WebView2 (included in Windows 11 and recent Windows 10 builds; setup downloads it when missing)

Architecture

Svelte 5 frontend --IPC (Session / SessionUpdate)--> Tauri v2 backend --> litediff-core

Three key decisions

• Send immutable session snapshots over IPC: the initial result includes both documents, while option-only recomputes use SessionUpdate and omit unchanged source text
• Single scroll authority: panels only report scrollTop; App stores one value and feeds it back to both panes so they stay pixel-aligned
• Collapse is a projection: buildDisplay() projects hunks into display items. Display indexes and source-line indexes are separate coordinate systems, so every jump must go through that projection

Testing

cargo test      # Rust
npm test        # Frontend (run from app/)

The core Rust guarantee is optimality validation: a brute-force DP LCS implementation serves as an oracle, asserting that the match count equals the LCS length across random low-alphabet inputs. This caught two intermediate-snake overlap bugs during development.

Known Limitations

Limitation	Reason
In-place editing	Conflicts with virtual scrolling, which recycles focused DOM nodes
Accept-change arrows	Require the in-place editing buffer model
Very large files	Whole-file comparison only; no chunked streaming yet