Kylmora

A native macOS browser. An AppKit shell over the system WebKit, one window with Spaces inside it, and no bundled engine or third-party dependencies. The whole app is a few hundred Swift files linking only Apple's frameworks, and the universal download is 6.1 MB.

kylmora.com

Status: a complete daily browser. Spaces with separate identities, sync, a command palette, automations, autofill, a PDF viewer, translation on the Mac's own model, extensions, content blocking and an optional AI assistant all work. Nothing in the UI is a mock: if a control is there, it does something, and a feature that cannot work on macOS says so instead of pretending. The assistant is off until you add a model of your own, and nothing is sent anywhere about you or your Mac.

Contributions are welcome — see Contributing.

Contents

• Install
• Features
• Requirements
• Building from source
• Project layout
• Driving it from outside
• Keyboard shortcuts
• Contributing
• Performance
• Where data lives
• Updates
• Name and icon
• License

Install

Download the latest build from the releases page: https://github.com/kylmora/kylmora/releases/latest (currently v0.1.65)

• Kylmora.dmg for people: open it and drag Kylmora to Applications.
• Kylmora.pkg for fleets: an installer a device-management tool can push silently.

Both are signed with a Developer ID and notarized by Apple, so they open without a security warning. Kylmora checks for new releases itself and can download them in the background; see Updates.

Prefer to build it yourself? See Building from source: macOS 14+ and a Swift 6 toolchain, no Xcode required.

Rolling it out to an organisation? docs/enterprise-policies.md covers deploying the .pkg through Jamf, Intune, Kandji and the rest, and locking settings across a fleet with a configuration profile or a policies.json. Samples are in Resources/Enterprise/.

Features

One window, many Spaces

• One window. Spaces and tabs switch inside it, never by opening another window. A vertical sidebar holds the omnibox, navigation, the active Space's tabs and the Space switcher; it can be always expanded, icons only, compact (slides in on hover), on the left or the right, or hidden. A horizontal tab bar above the page (⌃⌘B) is there for people who want tabs where every other browser puts them, and can be dragged to reorder.
• Spaces are identities. Each has its own cookies and logins, so the same site can be signed into as a different account in each one. A private Space writes nothing to disk and comes back empty on relaunch.
• A look per Space: light or dark, a colour or a gradient, a page's own theme colour on the chrome if the Space allows it, a solid, glass or gradient rim around the window so any corner of the screen says which identity is in front, a bookmarks bar, default fonts, full-screen behaviour. Export the whole look as a .kylmoratheme file and import it on another Mac.
• Per-Space settings on top of the look: downloads folder, bookmarks folder, which extensions run, password vault, proxy, search engine, user agent, tab sleep delay and default zoom.
• Space routing: rules that open matching addresses in a given Space, with an editor in Settings and a default for links arriving from other apps.
• Zen mode hides everything but the page. Compact mode, a keep-on-top window, window borders and a sidebar density setting (compact, regular, roomy) are all there.

Tabs

• Tabs are lazy: one that has not been shown has no web view and no WebKit process behind it. Background tabs sleep after an idle period and under memory pressure, and reopen where they were. Old tabs can be archived out of the sidebar on a schedule and brought back from the archive.
• Tab groups with names, emoji, icons and tints, nested; live folders that fill themselves from an RSS feed or a GitHub repository's issues and pull requests. Pinned sites per Space, and Essentials pinned across every Space.
• Per tab: rename, a colour tag, an emoji in place of the favicon, a note in the tooltip, keep awake, keep in sidebar, lock against closing, mute, auto reload every 10 seconds to 15 minutes. An unread dot appears when a page changes its title while its tab is out of sight; a ⧉ marks tabs another tab duplicates.
• Multi-select tabs, close duplicates, sort by title, domain or last use, reopen closed tabs, a tab overview grid (⇧⌘) with live thumbnails and search across every Space, and a task manager showing each tab's CPU and memory.
• Split view: side by side, stacked, or a 2×2 grid, with sticky panes. Glance peeks at a link over the page; Little Arc opens one in a small window of its own. Web panels dock a site beside the page, and a site can be installed as a standalone Dock app.
• Sessions restore on launch, including each tab's scroll position, form contents and back-forward history, without reloading from the network.

Getting around

• The command palette (⌘K or ⌘L) ranks open tabs, Spaces, history, bookmarks, commands and searches together as you type. Every feature is a command, and a custom command of your own can join them.
• Search engines with keywords and custom engines from any site's search box: g cats, !g cats and cats !g all search the engine whose keyword is g. A separate engine for private Spaces.
• New tabs open on a native start page: the Space's pinned and most visited sites as tiles, recently closed tabs and the unread reading list, drawn in the window with nothing fetched. The search engine's page or a homepage are the other choices.
• History with omnibox completion ranked by how often and how recently you visited, plus full-text search of page contents. Bookmarks with folders and tags, a bookmarks bar per Space, and a reading list with offline copies.
• Mouse gestures, rocker gestures, trackpad swipes, vim keys, link hints, and every keyboard shortcut customisable, including chords such as ⌘K then T. ⌘/ shows a cheat sheet of all of them.

Pages

• Reader mode, with Read Aloud, and a per-site "always use Reader".
• Page translation with Apple's on-device model (macOS 15 and later). The text never leaves the Mac, and the page updates as each part comes back.
• A PDF viewer of Kylmora's own: thumbnails, page number, zoom, search with a match count, rotate, Open in Preview and Save. Per site, choose Kylmora's viewer, WebKit's, a download, or Preview.
• Print and Page Setup through WebKit's own pagination, Export as PDF, View Page Source with line numbers, Copy as Markdown Link, Copy Title and URL.
• Screenshots of the visible area or the whole page, to a file or the clipboard, or into an editor with crop, arrows, boxes, circles, highlight, an irreversible blur and text.
• Boosts: your own CSS and JavaScript per site, and a universal dark mode. Picture in Picture on any video, automatically when you switch tabs if you like, and a native video player for sites whose own player fights you.
• Find in page with match marks on the scrollbar, zoom per site, JSON documents shown formatted, custom fonts and a minimum font size.

Content blocking and privacy

• Content blocking through WebKit's own content rule lists, fed by EasyList, EasyPrivacy, the cookie-banner lists and uBlock Origin's filters, fetched anonymously and on by default. Add your own lists and rules, pick an element on a page to block, and switch blocking off for one site.
• Cookie banners rejected automatically. Tracking parameters stripped from links. Hostile page behaviour undone: text made selectable, the right-click menu given back, the clipboard shielded.
• Anti-fingerprinting: canvas, WebGL and audio noise, hardware masking, randomised per Space. A custom user agent, globally, per Space or per site.
• Twenty-nine per-site settings, each with a default and per-site exceptions: Reader, auto-play, zoom, pop-ups, notifications, downloads, camera, microphone, screen sharing, location, content blockers, tracking prevention, cookies, JavaScript, web fonts, images, clipboard reading, referrer, certificate checks, user agent, compatibility mode, external apps, Picture in Picture, tab sleeping, forget when closed, native video player, anti-fingerprinting, hostile-behaviour protection, PDF documents.
• Website data manager, clear on quit with an allow-list, scheduled history and cookie removal, a RAM-only cache mode, a reset, and local crash reports you decide about. Touch ID or a master password can lock the browser.
• Encrypted DNS: Kylmora writes a system configuration profile for Cloudflare, Quad9, Google, AdGuard or a custom resolver, because page loads use the Mac's own DNS and only a profile can switch that to DNS over HTTPS. An HTTP or SOCKS proxy can be set globally or per Space.
• Favicons are fetched anonymously outside every Space, so the request carries no cookies and no identity. The address bar shows the page you are actually looking at, never a navigation that has not committed.

Passwords and forms

• Logins saved in the macOS login Keychain, the store Safari uses, so they sync with iCloud Keychain and Kylmora keeps no password database of its own. Offer to save, offer to fill, submit automatically, Touch ID before a fill.
• AutoFill for names, addresses and contact details from saved identities, and for payment cards whose numbers live in the Keychain: filled only on secure pages, after Touch ID, never submitted, and the security code is never stored.

Automations

• Rules that act when a page loads, a tab sits idle, media starts playing or a download finishes: move to a Space, pin, mute, keep awake, open in Reader, set zoom, archive, close, show a message, open an address, run an Apple Shortcut or an AppleScript. Rules export and import as JSON.
• A rule set to run from the command palette is a custom command, with a keyboard shortcut of its own if you want one.

AI assistant and agent

• Assistant panel: the sparkles button at the top right of the window opens a chat beside the page. Ask about what you are reading, or have it do something on the page for you.
• Bring your own model: Claude in Anthropic's format, or any server that speaks the OpenAI format -- OpenAI, OpenRouter, Groq, a model on the Mac through Ollama or LM Studio, or a custom address. Presets fill in the address; any model ID can be added. Keys are kept in the login Keychain and sent only to the server of the model they belong to. A model running on the Mac needs no key.
• It uses the page like a person: the agent works in the Space you are in, with that Space's logins, and acts with real mouse and keyboard input from a cursor you can watch. Take over at any moment. At a sign-in, captcha, two-factor code or payment it stops and hands the page to you, and it is told to ask before anything that cannot be undone.
• The same agent is open to tools outside the app: see Driving it from outside.

Task Manager

• What every Space and page is costing in memory, processor and graphics, live, with two minutes of history. Put a page to sleep, reload or close it from the list. On the Window menu, on ⇧⌘U, in Settings, and optionally as a gauge in the sidebar's footer.

Extensions, sync and import

• Extensions on WebKit's own extension engine, which reads the manifest format Chrome and Firefox extensions use: paste a Chrome Web Store or addons.mozilla.org link in Settings, or install a .zip, .crx, .xpi or an unpacked folder (macOS 15.4 and later). Enable them per Space.
• Side panels: extensions that put their interface beside the page rather than in a popup work, in both spellings -- Chrome's chrome.sidePanel and Firefox's browser.sidebarAction. WebKit's engine has neither, so Kylmora provides the API and the panel: docked beside the page, following the tab, opened by the extension's own button. See docs/extension-side-panels.md.
• Native messaging: an extension can talk to an app installed on the Mac, which is what a password manager's extension is for -- the vault lives in the app and the extension is a front end. Kylmora reads the host manifests apps install for Chrome and Firefox as well as its own, because almost no app ships one for Kylmora, and the app's own manifest still decides which extensions may reach it. Settings ▸ Extensions lists what is installed, says why a manifest was refused, and can switch any of it off. See docs/native-messaging.md.
• Extension blocking rules: an MV3 content blocker's declarativeNetRequest rules are read, translated and enforced by WebKit's own matcher. WebKit's extension engine does not implement the API, so such a blocker otherwise installs, looks healthy and blocks nothing. Rules that cannot be translated are reported rather than dropped quietly. See docs/declarative-net-request.md.
• Web notifications: a page that calls Notification or a service worker's showNotification gets a real macOS notification, and clicking it comes back to the tab that sent it -- switching Space if need be. WebKit defines the API in a WKWebView and attaches nothing behind it, so Kylmora provides both the API and the delivery. Per-site, from the Websites pane. See docs/web-notifications.md.
• Sync through iCloud, Google Drive, Dropbox, OneDrive, Nextcloud or WebDAV, or any folder: open tabs, bookmarks, website settings and rules, and optionally the last 2,000 visits of history. With a passphrase the archive is encrypted end to end before it leaves the Mac, and only then can saved passwords travel with it; they never go to CloudKit. Export and import the whole sidebar as a backup.

For organisations

• Nineteen policies delivered by MDM configuration profile or a policies.json: homepage, new tab, search engine, URL block and allow lists, extensions, developer tools, private browsing, the password manager, content blocking, native messaging, updates, a DNS resolver, a RAM-only cache. Kylmora ▸ Enterprise Policies… shows what is in force. See docs/enterprise-policies.md.

Requirements

• macOS 14 (Sonoma) or later, for per-Space WKWebsiteDataStore. Page translation needs macOS 15; extensions need macOS 15.4.
• To build: a Swift 6 toolchain. Xcode is not required. The Command Line Tools are enough (xcode-select --install).

Building from source

Everything goes through the Makefile:

make run      # build, bundle and launch build/Kylmora.app
make bundle   # build the app bundle without launching
make pkg      # wrap the bundle in an installer package (after make bundle)
make test     # run the unit test suite
make size     # report the release bundle size
make measure  # launch and report launch time, memory and bundle size

There are no dependencies to fetch first; the project links only Apple system frameworks. Releases are cut by CI from a vX.Y.Z tag, which becomes the app's version.

Project layout

Sources/Kylmora/
├── Application/      App delegate, menus, launch, updates, the kylmora:// scheme
├── Window/           The single main window and its chrome
├── Sidebar/          The vertical sidebar (tabs, spaces, actions)
├── UI/               Chrome views: command bar, rows, tab bar, toolbar layout, styling
├── Tabs/             Tab model, lazy web views, suspension, archiving
├── Spaces/           Spaces, looks, window borders, theme files
├── StartPage/        The native new-tab page
├── Session/          The in-memory browser model and change notifications
├── Storage/          Session JSON, SQLite history/bookmarks, app paths
├── Web/              WebKit environment, navigation, error pages, printing
├── PDF/              The PDF viewer and its inline fetch
├── Automations/      Rules: triggers, actions, the engine and the service
├── Assistant/        The AI chat panel, model settings and the two API formats
├── Agent/            The agent: real input, the cursor overlay, hand-off, its local server
├── Diagnostics/      The Task Manager: per-tab metrics, charts, history
├── Routing/          Space routing rules
├── Passwords/        Keychain logins, identity and card autofill
├── Downloads/        Download manager, list, destinations
├── Folders/          Tab groups and live folders
├── ContentBlocking/  Filter lists compiled to WebKit content rules, element picker
├── Sites/            Per-site settings and the scripts that enforce them
├── Extensions/       WebKit extension engine integration
├── Sync/             Sync archives, merge, providers, importers
├── Screenshot/       Capture and the annotation editor
├── Translation/      Apple's on-device translation, driven from AppKit
├── Shortcuts/        Customisable shortcuts, chords, the cheat sheet
├── Settings/         The Settings window and its panes
├── Enterprise/       Managed policies
└── ...               Reader, Split, Glance, LittleArc, WebPanels, Boosts, Security, Network, Gestures, Keyboard, TabOverview
Tests/KylmoraTests/   The swift-testing suite
Tools/                make-icon.py, measure.sh, notarize.sh, the kylmora command-line tool

Driving it from outside

The app registers the kylmora:// scheme, and a command-line tool ships inside the bundle. Link it onto your PATH once:

ln -s /Applications/Kylmora.app/Contents/Resources/kylmora-cli /usr/local/bin/kylmora
kylmora open https://example.com --space Work --background
kylmora space Personal
kylmora command print-page      # any command palette id
kylmora new-tab
kylmora url open https://a.b    # print the kylmora:// address instead

The same tool drives the AI agent, for a coding agent or a script on the Mac. It works in a Space you choose, with real input you can watch:

kylmora agent profiles              # Spaces and their logins
kylmora agent open https://example.com --profile Work
kylmora agent snapshot              # the page's elements, each with an @ref
kylmora agent click @12 --label "Open the menu"
kylmora agent type "hello" --ref @7
kylmora agent handoff "Please sign in"   # give the page to the person
kylmora agent mcp                   # serve the same tools over MCP (stdio)

Anything that can run open can use the addresses directly: open "kylmora://tab?url=https://example.com&space=Work". Automations can run Apple Shortcuts and AppleScripts the other way round.

Keyboard shortcuts

The defaults. Every one can be changed in Settings ▸ Shortcuts, and ⌘/ lists them all.

Shortcut	Action
Cmd-K or Cmd-L	Command palette
Cmd-T	New tab
Cmd-W	Close tab
Cmd-Shift-T	Reopen closed tab
Cmd-R	Reload
Cmd-.	Stop loading
Cmd-F	Find in page
Cmd-G / Cmd-Shift-G	Find next / previous
Cmd-P	Print
Cmd-D	Add or remove a bookmark
Cmd-Shift-D	Add to reading list
Cmd-Shift-R	Reader mode
Cmd-Opt-T	Translate page
Cmd-Opt-L	Downloads
Cmd-[ / Cmd-]	Back / forward
Cmd-Opt-Right / Left	Next / previous tab
Cmd-Opt-Down / Up	Next / previous Space
Cmd-1 … Cmd-9	Select tab by position, 9 being the last
Cmd-Shift-\	Tab overview
Cmd-Opt-V / Cmd-Opt-Shift-H / Cmd-Opt-G	Split side by side / stacked / 2×2
Ctrl-Cmd-S	Toggle the sidebar
Ctrl-Cmd-B	Show or hide the tab bar above the page
Ctrl-Cmd-Z	Zen mode
Ctrl-Cmd-F	Full screen
Cmd-Opt-Shift-3 / 4	Capture visible area / full page
Ctrl-Opt-Cmd-3 / 4	Capture and annotate
Cmd-Opt-Shift-U	View page source
Cmd-/	Keyboard shortcuts cheat sheet
Cmd-,	Settings

Contributing

Contributions of every kind are welcome: bug reports, feature ideas, documentation, tests and code. The short version:

1. Read the Contributing guide and the Code of Conduct.
2. For anything non-trivial, open an issue first to agree on the approach.
3. Fork, branch off main, make your change, and keep make test green.
4. Open a pull request describing what you changed and why.

New here? Issues labelled good first issue are a friendly starting point. The full guide covers setup, the project's code-style principles (Swift 6 strict concurrency, system frameworks only, no "fake" UI), and the review process. What is not built yet is in docs/roadmap.md, and where Kylmora stands against the nearest comparable browser -- what has been closed, and what this engine simply cannot do -- is in docs/competitive-gap-status.md.

Performance

Measured with make measure on 2026-09-19 against v0.1.63, Apple silicon, macOS 26.6. Memory is physical footprint, the number Activity Monitor shows.

Memory here is the whole browser, not Kylmora's process: the UI process plus every WebKit process working for it. Pages render in WebKit content, network and GPU processes that are XPC services parented to launchd, so quoting Kylmora's own process reports a fraction of what the browser costs. It is a true number that gives a false impression, and a reader with Activity Monitor open will say so. make measure attributes those services by the client bundle id each one writes into its own cache and temp directory, which is exact rather than inferred.

Metric	Value
Universal download	6.1 MB, installs to 12.2 MB
Apple-silicon-only download	3.1 MB, installs to 5.8 MB
Bundled frameworks, package dependencies	0, 0
Window on screen, warm	0.62 s
Whole browser, one tab	99 MB
Whole browser, 31 tabs restored, one shown	502 MB
Kylmora's own process in that state	66 MB
Whole browser, 5 Reddit tabs all opened	1,783 MB
The same 5 tabs after a restart, one shown	479 MB

The last two rows are the point. A live page costs about what it costs in Safari, because it is the same engine; Kylmora cannot make a page cheaper. What it does is decline to pay for tabs nobody has looked at: a restored tab has no web view until it is shown, which is the whole difference between 1,783 MB and 479 MB. The app's own log states it directly, tabs=31 loaded=1.

Most of the time before the window is the system loading the binary and the frameworks it links. Sync, live folders, timers, housekeeping and the update check start only after the window has drawn.

An earlier version of this table quoted a 5.2 MB bundle, which was the Apple-silicon slice rather than the build the download button hands you, and 38 MB and 58 MB for the browser process, which excluded the pages. Both are corrected above rather than quietly restated. Figures not re-measured on 2026-09-19 have been dropped instead of carried forward.

Where data lives

Everything is keyed by the bundle identifier, com.kylmora.Kylmora, under ~/Library/Application Support/com.kylmora.Kylmora/:

• session.json — Spaces, tabs, and each tab's saved interaction state
• browser.sqlite — history, its full-text index, and bookmarks
• downloads.json — the downloads list, capped at 100 rows
• site-settings.json, space-routing.json, automations.json, shortcuts.json, boosts.json, autofill.json, live-folders.json, webapps.json — the corresponding settings, each a readable JSON file
• filter-lists/, extensions/, Favicons/, WebApps/, Updates/, CrashReports/, Sync/ — caches and packages

Logins and card numbers are in the login Keychain, not in any file here. Every Space after the first keeps its website data in ~/Library/WebKit/com.kylmora.Kylmora/WebsiteData/<uuid>/, managed by WebKit; the first Space uses WebKit's default store. Downloaded files go to ~/Downloads or the folder a Space chooses. Preferences live in UserDefaults under com.kylmora.Kylmora.

Updates

Settings ▸ About shows the version and checks for updates. With automatic checks on, Kylmora asks https://kylmora.com/releases/latest.json once a day, a document of the form {"version": "0.2.0", "url": "https://kylmora.com/download", "notes": "…"}, and can download the new build in the background and offer to install it. A version can be skipped. The request carries nothing about you or your Mac. After an update, a note says which version this now is and links to its release notes.

Name and icon

The app icon is built from the blue K mark at Resources/Icon/kylmora-mark.png by Tools/make-icon.py, which places it on a white rounded square on Apple's icon grid and writes Resources/Kylmora.icns. make bundle regenerates the icon when the mark or the script changes.

License

Licensed under the Apache License 2.0. By contributing, you agree that your contributions will be licensed under it as well.