Northstar web browser

Northstar is a minimalist web browser written from scratch in C. Its engine targets practical HTML5, modern CSS and JavaScript compatibility without embedding Gecko, WebKit, Blink or another browser engine. Linux is the primary platform; macOS and Windows are also supported.

This repository is the open-source GPL edition of the Nordstjernen project. Northstar is licensed under the GNU General Public License, version 3 or later.

Web standards: Behaviour is measured against the specification text, section by section, not against another browser. The engine runs web-platform-tests through headless mode; see docs/compliance.md for the current per-area scores and the known structural gaps.

Security: on Linux the browser runs behind a Landlock filesystem sandbox (plus PR_SET_NO_NEW_PRIVS), with a default-deny seccomp syscall filter in both GUI and headless/tooling modes · no JIT. See SECURITY.md for the exact per-mode posture.

Minimalism: one window, one page, one process. The engine is a compact body of C — about 160,000 lines of original C (excluding the vendored WAMR, Wuffs and audio decoders, and the generated image-data tables) — small enough for one person to read and audit end-to-end.

What this edition is

This edition strips Northstar down to a single-window, single-page, single-process desktop browser, based on the Nordstjernen project. It deliberately omits tabs, per-tab renderer processes, WebGL, WebGPU, an embedded PDF viewer and AI-style web APIs. It does not send telemetry or update pings.

Audio still plays in-process (MP3, MP2, Ogg Opus/Vorbis). Images decode in-tree (PNG/APNG, GIF, BMP, JPEG and WebP via Wuffs, AVIF through libavif when available, and SVG in the engine).

Browser features

• HTML parsed to a DOM by lexbor; CSS by the engine's own cascade — flex, grid, transforms, gradients, @keyframes, scroll snap.
• JavaScript on the QuickJS interpreter — DOM, Shadow DOM, observer APIs, Canvas 2D (Path2D, ImageBitmap, DOMMatrix), WebCrypto (crypto.subtle over OpenSSL).
• Custom elements — autonomous and customized built-in elements.
• Workers — dedicated workers with structured-clone messaging, message channels and broadcast channels.
• Storage — IndexedDB over SQLite, localStorage/sessionStorage and the cache API, each partitioned by origin.
• Live connections — WebSockets and server-sent events.
• Navigation API — window.navigation for single-page routing.
• Service workers — origin-scoped registration, persistence and controlled-page fetch interception.
• WebExtensions — installed local extensions with manifest content scripts, safe packaged resources, local storage and runtime messaging.
• Networking over HTTP/2 with libcurl — HTTP/3 when the linked libcurl provides it — HSTS, CSP, subresource-integrity (SRI) checks, partitioned cookies.
• Safe browsing — before a top-level navigation is fetched, its host is checked against a local SHA-256 blocklist. The check runs entirely on-device.
• Media — images (PNG/APNG, GIF, BMP, JPEG, WebP, optional AVIF, SVG); audio (<audio>) decodes and plays in the browser process, alongside a Web Audio graph. <video> plays MPEG-1 (video/mpeg), decoded in-tree by the same pl_mpeg that already handles MP2 audio. MPEG-1 is an ISO standard whose patents have expired, so it costs no dependency and no licence; it is also not a format the modern web serves, so this is video support for local and self-hosted clips rather than for streaming sites.
• Printing — Ctrl+P lays the page out for paper and hands the sheets to the operating system's own print dialog through GtkPrintOperation: CUPS on Linux, the Win32 dialog on Windows, the Cocoa panel on macOS. @media print matches, @page sets the sheet size and margins, and break-before / break-after / break-inside decide where a sheet ends.
• MathML — a minimalist presentation-MathML renderer.
• Spell checking — optional, via the Enchant library.
• WebAssembly — the JavaScript API over a vendored WAMR interpreter.
• Single window / single process — the browser shows one page in one window, and the page engine runs in the shell process (no per-tab renderer processes).
• UI — bookmarks, find-in-page, printing, save-to-PDF, JS console, settings, headless mode.

Build and run

On Debian or Ubuntu, install the required development packages:

sudo apt install build-essential pkg-config meson ninja-build cmake \
    libgtk-4-dev libcurl4-openssl-dev libssl-dev libuchardet-dev \
    libharfbuzz-dev libfribidi-dev libcairo2-dev libfontconfig-dev \
    libfreetype-dev libpsl-dev libsqlite3-dev libseccomp-dev libsdl2-dev \
    zlib1g-dev
meson setup builddir
meson compile -C builddir
./builddir/src/gtk/northstar

The development helper configures the default build directory when needed and runs the same compile command:

./scripts/dev.sh build
./scripts/dev.sh smoke

The smoke command renders deterministic local fixtures through the headless engine and compares them with the checked-in baselines. A single page can also be rendered directly:

./builddir/src/gtk/northstar --headless --dump=text about:start

Meson feature options include -Davif=disabled, -Daudio=disabled, -Dwasm=disabled and -Dgtk=disabled for smaller or engine-only builds.

WAMR, Wuffs, pl_mpeg and minimp3 are vendored in-tree. ns-pango, lexbor and quickjs-ng are pinned upstream subprojects (see subprojects/*.wrap) that meson setup fetches; see docs/building.md for how a pin is moved.

Dependencies

Northstar's engine is written from scratch — it contains no forked browser engine (no Gecko, WebKit, or Blink). It is the GPL edition of the Nordstjernen project.

Pinned upstream meson subprojects (subprojects/*.wrap), fetched by meson setup:

lexbor and quickjs-ng take a system copy instead when the build finds one new enough; ns-pango is always the subproject, since the fork's renamed symbols are what let it coexist with the system Pango that GTK loads.

Vendored in-tree (built from the main tree, no submodules):

Required system libraries: GTK 4 (≥ 4.14; ≥ 4.22.1 on Windows), GLib/Cairo, HarfBuzz, FriBidi, fontconfig, FreeType, libcurl (≥ 8.5), OpenSSL (libcrypto), uchardet, libpsl, SQLite and zlib. The engine lays text out through ns-pango rather than the system Pango; GTK still links the system Pango for its own widgets, and the two coexist because every symbol in the fork is renamed. Linux builds also require libseccomp. SDL2 is required when in-process audio is enabled.

Optional (auto-detected): libavif (AVIF images), opusfile / vorbisfile (in-process Ogg audio), Enchant (spell-checking) and libthai (Thai line breaking).

License

Northstar is free software, licensed under the GNU General Public License, version 3 or later — see LICENSE.

Project home: https://nordstjernen.org · Copyright 2026 Andreas Røsdal.

Builds