isa

A blazingly fast, minimalist, memory-efficient macOS web browser.

Features · Install · Build from Source · Shortcuts

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isa is a lightweight, open-source web browser built natively for macOS using Swift, SwiftUI, AppKit, and WebKit (WKWebView). Engineered specifically to solve the extreme memory hogging and battery drain of Chromium and Electron browsers, isa combines an intelligent tab-decay engine, shared WebKit process pooling, built-in network and cosmetic ad blocking, YouTube video ad defusal scriptlets, and a distraction-free Zen interface.

No accounts. No telemetry. No background bloat. Just the web, at native speed.

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Features

Intelligent Memory Management & Performance

• Aggressive Tab Decay: Inactive tabs automatically enter deep sleep after idle timeouts, releasing their underlying WebContent processes and reclaiming memory.
• Shared WKProcessPool: All tabs share a unified WebKit process pool, reducing process duplication across multiple open pages.
• Concurrency Limiting: Background tabs do not spin up heavy WebContent processes until focused, avoiding memory spikes when opening batches of tabs.
• Instant Tab Restoration: Sleeping tabs retain their title, address, favicon, and state, restoring effortlessly when brought to the foreground.
• Auto-Play Suppression: Inactive tabs are prevented from decoding video and buffering audio before user interaction.

Native Ad & Tracker Blocking

• Network Request Blocking: Over 145,000 compiled rules from EasyList and EasyPrivacy compiled into native WKContentRuleList bytecode, blocking ads, analytics, trackers, and fingerprinting scripts before network transmission.
• Cosmetic Element Hiding: Injects domain-targeted CSS rules at document_start to collapse empty ad banners, sponsors, and cookie prompts without Flash of Unstyled Content (FOUC).
• YouTube In-Stream Video Ad Defusal: Built-in uBlock Origin-compatible scriptlet pipeline hooks ytInitialPlayerResponse and fetch/XHR player endpoints to eliminate prerolls and midrolls.
• Full CSP & Trusted Types Compliance: Injected scripts avoid eval() or dynamic script generation, safely adhering to strict site security policies.
• One-Time Bytecode Compilation: Rules compile once to disk; startup requires only ~22 MB of host memory and zero per-tab compilation overhead.

Zen Mode & Distraction-Free UI

• Flexible Tab Layout: Toggle instantly between a modern Left Sidebar and classic Top Bar tabs (Cmd+Option+T).
• Collapsible Sidebar: Collapse the tab bar to maximize your viewable webpage area.
• Animated Theme Switching: Fluid toggle between Light, Dark, and System appearances with smooth spring physics.
• Minimalist Chrome: Hidden titlebar, clean URL overlay, and distraction-free navigation.

Tab & Window Controls

• Persistent Pinned Tabs: Pin critical tabs (Cmd+Shift+P); pins automatically persist across app launches.
• Per-Tab Audio Muting: Instantly silence noisy background tabs from the tab item or using Cmd+Shift+M.
• Drag-and-Drop Reordering: Smooth tab drag-and-drop support with animated reordering.
• Numbered Tab Selection: Jump directly to any of your first 9 tabs with Cmd+1 through Cmd+9.

Built-in Essentials

• In-Page Find Bar (Cmd+F): Native search overlay with real-time match counts, instant highlights, and keyboard traversal (Enter / Shift+Enter).
• Download Manager: Native floating downloads popover with progress bars, Finder reveals, and cancellation.
• Searchable History (Cmd+Y): Fast browsing history with instant search filtering, date grouping, and one-click history clearing.
• Customizable Shortcuts (Cmd+/): Comprehensive shortcut manager and HUD for keyboard-first navigation.

Privacy-First

• Zero analytics, telemetry, or remote crash reporters.
• No mandatory accounts, logins, or cloud syncing.
• Your browsing data stays entirely on your local machine.

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Memory Audit & Benchmarks

Audits measured against 25 active tabs:

Scenario	Live WebContent Procs	WebKit Total RSS	Host App RSS
1 active tab (idle)	1 proc	~151 MB	~134 MB
2 active tabs (idle)	2 procs	~178 MB	~142 MB
25 tabs with tab decay enabled	2 procs (23 sleeping)	~178 MB	~156 MB
Typical Chrome / Arc (25 tabs)	20–25 procs	2,500–4,500 MB	400–800 MB

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Keyboard Shortcuts

Shortcut	Action
Cmd + T	New Tab
Cmd + W	Close Active Tab
Cmd + 1 .. Cmd + 9	Select Tab 1 through 9
Cmd + L	Focus Address Bar
Cmd + R	Reload Page
Cmd + [ / Cmd + ]	Navigate Back / Forward
Cmd + F	Find in Page
Cmd + G / Cmd + Shift + G	Find Next / Previous Match
Cmd + Shift + M	Mute / Unmute Active Tab
Cmd + Y	Show Browsing History
Cmd + Option + T	Toggle Tab Placement (Sidebar / Top)
Cmd + Shift + B	Run 25-Tab Benchmark Sequence
Cmd + Shift + U	Open 25 Sample Tabs

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Install

Download Pre-Built DMG

Download the latest release from the Releases page. Open isa.dmg and drag isa.app to your Applications folder.

Requirements

• macOS Sonoma (14.0) or later
• Apple Silicon (M1/M2/M3/M4) or Intel Mac

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Build from Source

Prerequisites

• macOS 14.0+
• Xcode 15.0+ or Command Line Tools
• Swift 5.0+
• Rust toolchain (optional, only required if rebuilding the adblock converter)

1. Clone the repository

git clone https://github.com/drunkardleo/isa.git
cd isa

2. Build Debug Application

make build

Or directly with xcodebuild:

xcodebuild -project isa.xcodeproj -scheme isa -configuration Release build

3. Package DMG

make dmg

The resulting isa.dmg will be created in your root directory.

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Developer Tooling

Updating Adblocker Rules

The adblocker rules and cosmetic scripts are compiled ahead of time into rules/ using an offline Rust CLI powered by the adblock engine.

To fetch the latest EasyList, EasyPrivacy, and uBlock Origin rule lists and compile them:

./generate_rules.sh

This script:

1. Downloads the latest rule sets from upstream repositories.
2. Uses tools/rule-converter to transform ABP syntax into WebKit content-blocking JSON rules and domain-specific cosmetic CSS.
3. Validates compilation against WebKit's native WKContentRuleListStore.
4. Outputs optimized JSON to rules/content-blocker.json, rules/cosmetic-filters.json, and rules/scriptlets.json.

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Tech Stack

Component	Technology
App Framework	Swift 5.0, SwiftUI, AppKit
Web Engine	WebKit (WKWebView, WKProcessPool, WKContentRuleListStore)
Project Management	XcodeGen (project.yml) & Xcode Project
Rule Compiler	Rust (tools/rule-converter using adblock crate)
Styling & Assets	SF Symbols, Custom Vector SVGs, xcassets

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Contributing

Contributions, bug reports, and suggestions are welcome!

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Test your changes thoroughly
4. Commit your changes (git commit -m 'Add amazing feature')
5. Push to the branch (git push origin feature/amazing-feature)
6. Open a Pull Request

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License

This project is licensed under the MIT License — see the LICENSE file for details.