Last verified
Browse the web on macOS from a sidebar-first layout with vertical tabs, built-in content blocking, on-device AI via Apple Intelligence, and GPL-3.0 source.
Nook's DevMCPServer lets a local coding agent control the browser through an MCP endpoint. The agent can navigate pages, read DOM content, and interact with tabs without the developer switching focus. The integration is native to the app, not a browser extension.
Your workflow does not involve a local MCP-compatible coding agent, or you develop on Windows or Linux. Nook is macOS and Apple Silicon only.
NookBlocker removes ads and cosmetic residue at the WebKit level on every page load, without requiring a separate extension install or a browser store account. The blocker's filter lists and cosmetic rules are part of the app's open source codebase.
You need a large browser extension ecosystem. Nook supports WKWebExtensions but the catalog is smaller than Chrome's or Firefox's. Extensions relying on Chrome-specific APIs will not work.
Arc stops working on December 22, 2026. Nook provides the same vertical tab, sidebar-first, spaces-based layout that Arc popularized, under a GPL-3.0 license, on an Apple Silicon Mac. Export your Arc data before mid-December and switch to Nook if the sidebar model is what you need on macOS.
You use Arc on Windows or iOS, or you rely on Arc's collaboration features or shared links. Nook is macOS and Apple Silicon only and does not replicate those integrations. Windows users and iOS-only Arc users need a different replacement.
Nook's package-based Swift architecture separates the blocker, tweak engine, AI manager, and UI into distinct local Swift packages. Anyone with Xcode can read the content blocker logic, modify the site tweaks, or add a new AI provider to AIManager without touching the rest of the app.
You do not have an Apple Silicon Mac and Xcode 26. Building from source requires both.
Browser tabs accumulate faster than you can manage them. The horizontal tab bar most browsers use gives each open page the same visual weight, with no hierarchy, no grouping, and no quick way to see which spaces hold which context. Power users end up with dozens of tabs open and no structure for them.
Commercial browsers with better tab management, like Arc and Dia, addressed this with sidebar-first designs, but both are proprietary products. Arc stops working on December 22, 2026, and new Arc accounts can no longer be created. If you rely on Arc's sidebar layout today, you need an open source path forward.
Vertical tabs live in a persistent sidebar panel, not a tab bar. Tabs are organized into spaces using the NookTabsCore model, each with its own item tree and ordering. This keeps related context grouped and visible without opening a separate window manager.
NookBlocker integrates adblock-rust and a cosmetic filtering engine directly into the browser at the WebKit level. Filter lists refresh via CI scripts. Cosmetic filtering removes page-level layout artifacts such as empty divs and ad containers that basic blockers skip. No extension store account needed.
On macOS 26 with Apple Intelligence enabled, the AI chat panel runs entirely on-device. No prompt data leaves the machine. The AIManager also supports external AI providers and an MCP client for connecting the browser to coding tools or external AI endpoints.
TabOrganizerManager groups open tabs by topic using Apple's MLX framework, running the model locally on Apple Silicon. Tab data never goes to a remote server. Requires macOS 26 and Apple Intelligence enabled; the MLX dependency has no x86_64 build.
NookTweaks ships native improvements for YouTube, Facebook, and other sites, including SponsorBlock integration and custom routing rules. These are built into the app as a native Swift package, not browser extensions, so they cannot be disabled by extension permission policies.
DevMCPServer exposes a local MCP endpoint so a coding agent running in a terminal can drive the browser: navigate to URLs, read page content, and interact with the active tab. Useful for AI-assisted development workflows where the agent needs browser access alongside code.
Both Nook and Arc use a sidebar-first tab model where spaces and vertical navigation replace the horizontal tab bar. Arc was created by The Browser Company; the Nook repo description references Arc's acquisition history directly ("A new browser, not owned by Atlassian"). Arc stops working on December 22, 2026 and new accounts can no longer be created.
| Feature | Nook | Arc |
|---|---|---|
| Status | Active, new maintainer since September 2026 | Stops working December 22, 2026 |
| License | GPL-3.0 | Proprietary |
| Source available | Yes (full) | No |
| Platform | macOS, Apple Silicon | macOS, iOS, Windows (separate app) |
| AI features | On-device via Apple Intelligence | Cloud-based |
| Extension support | WKWebExtensions | Chrome extensions |
| Content blocking | Built-in (adblock-rust) | Extension-dependent |
If you are on Arc today: stay through the shutdown if your setup holds, export your data before mid-December, then switch to Nook for the sidebar-first layout on an Apple Silicon Mac. Nook is not a substitute for Arc on Windows (Arc for Windows was a separate desktop app) or iOS; those users need a different replacement. See the Arc alternatives guide for a full comparison across platforms.
Dia is a newer AI-native browser from The Browser Company. Like Nook, it uses a sidebar-first design, but its AI features are cloud-connected and its code is proprietary.
| Feature | Nook | Dia |
|---|---|---|
| License | GPL-3.0 | Proprietary |
| Source available | Yes | No |
| AI model execution | On-device (Apple Intelligence, MLX) | Cloud-connected |
| Platform | macOS, Apple Silicon | macOS |
| Content blocking | Built-in (adblock-rust) | Extension-dependent |
Nook is the stronger choice for users who want on-device AI without sending tab context to a remote server: the tab organizer and AI chat run locally via MLX and Apple Intelligence. Dia is worth considering when you need cloud-connected AI that works across contexts and sessions, or Dia-specific integrations with no open source equivalent.
Nook ships pre-built for Apple Silicon. Download and install from GitHub Releases (macOS 15.5 or later, Apple Silicon required):
https://github.com/nook-browser/Nook/releases/latest
Open the downloaded DMG and drag Nook to Applications. To build from source instead (macOS 15.6 + Xcode 26, see FAQ):
```bash
git clone https://github.com/nook-browser/Nook.git
cd Nook && open Nook.xcodeproj
```No. Nook builds for Apple Silicon only because the on-device tab organizer uses MLX, which has no x86_64 build. Pre-built releases and the build-from-source path both require Apple Silicon. Intel Mac users cannot run the current version.
The pre-built app requires macOS 15.5 (Sequoia) or later. Building from source requires macOS 15.6 and Xcode 26. On-device AI chat and the tab organizer need macOS 26 with Apple Intelligence enabled. Users on macOS 14 or earlier cannot run the app.
Yes. Nook is licensed under GPL-3.0, meaning its full source is public, forkable, and any distributed derivative must also release source. Arc is a proprietary app with no public source. The Nook repo description notes it is "A new browser, not owned by Atlassian," a reference to Arc's acquisition history.
NookBlocker is a native Swift package built on adblock-rust with a cosmetic filtering engine. It blocks at the WebKit level, not through a JavaScript extension, so it cannot be disabled by an extension permission policy and handles cosmetic residue such as empty divs and ad containers that standard blockers skip.
Yes, Nook supports WKWebExtensions, Apple's browser extension standard for macOS. The catalog is smaller than Chrome's or Firefox's. Extensions built on Chrome-specific APIs or Manifest V2 features will not work. Core browsing features like content blocking and site tweaks are built into the app and do not require extensions.
#1 in the Arc guide
Sidebar Workspaces, split view for up to 4 tabs and Boosts, the closest match to how Arc worked
#2 in the Arc guide
Workspaces that switch a Firefox container per project, with no account required
#3 in the Arc guide
Chrome Web Store extensions and an Android app, with encrypted sync across devices
#4 in the Arc guide
Vertical tabs, tab groups and split view built into the browser itself, on 5 platforms
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