Northstar Browser
Northstar is a minimalist web browser written from scratch in C. One window, one page, one process — about 149,000 lines of original C, small enough for one person to read and audit end-to-end. It carries no upstream browser engine: no Gecko, no WebKit, no Blink. It is free software under the GNU General Public License, version 3 or later, and it runs on Linux, macOS and Windows.
Northstar Browser version 1.0.6 released! A rebuilt CSS grid, an indexed cascade, faster text layout, Web Audio that actually renders, and relative colour syntax. Read the announcement · More info here.
about:start page — one window, one page, and a search box. more screenshots »Free software. Licensed under the GNU GPL, version 3 or later — use it, read it, change it, share it. The whole engine is in the repository at github.com/nordstjernen-web/northstar-browser.
Written from scratch. Every behaviour is implemented in the project's own C — the parser glue, the cascade and value parsing, layout, paint, and the DOM and CSSOM bindings. Compliance is not inherited from an upstream engine; it is measured, section by section, against the specification text.
One window, one page, one process. All rendering happens in a single compact process, prioritizing auditability over the isolation a multi-process browser buys. On Linux it runs behind a Landlock filesystem sandbox (plus PR_SET_NO_NEW_PRIVS) with a default-deny seccomp syscall filter, in both GUI and headless modes. There is no JIT.
Private by construction. No telemetry, no update pings, and no AI assistant or AI-style web APIs. Safe browsing checks a top-level navigation's host against a local SHA-256 blocklist before it is fetched — the check never leaves your machine. Cookies, storage and the cache are partitioned by origin.
what it does
- HTML and CSS. HTML is parsed to a DOM by lexbor; CSS goes through the engine's own cascade — flex, grid, transforms, gradients,
@keyframes, container queries, relative colour syntax and thecolor()function across nine colour spaces. - JavaScript. quickjs-ng, a bytecode interpreter with no JIT — DOM, Shadow DOM, observer APIs, Canvas 2D (
Path2D,ImageBitmap,DOMMatrix) and WebCrypto (crypto.subtleover OpenSSL). - Custom elements — autonomous and customized built-in elements, with the insertion steps that make
connectedCallbackfire however the element was inserted. - Workers — dedicated workers with structured-clone messaging, message channels and broadcast channels, sharing the storage partition of the page that started them.
- Storage — IndexedDB over SQLite,
localStorage/sessionStorageand the cache API, each partitioned by origin. - Live connections — WebSockets and server-sent events; the Navigation API (
window.navigation) for single-page routing; and service workers with 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, reached through the alt-svc cache rather than by stalling on a QUIC connect — with HSTS, CSP, subresource-integrity checks and partitioned cookies.
- Images — PNG/APNG, GIF, BMP, JPEG and WebP decode through Wuffs, AVIF through libavif when available, and SVG is rendered in-engine.
- Media —
<audio>decodes and plays in the browser process (MP3, MP2, Ogg Opus/Vorbis) alongside a Web Audio graph.<video>plays MPEG-1, decoded in-tree by the same pl_mpeg that handles MP2 audio — an ISO standard whose patents have expired, so it costs no dependency and no licence. - WebAssembly — the JavaScript API over a vendored WAMR interpreter. MathML — a minimalist presentation-MathML renderer. Spell checking — optional, via Enchant.
- The browser itself — bookmarks, find-in-page, save-to-PDF, history, a JavaScript console, settings, page zoom, a dark theme that follows the desktop, and a headless mode used for testing and for rendering a page from the command line.
what it leaves out
Northstar is deliberately smaller than Nordstjernen, the source-available flagship built from the same engine. It has no multi-window or multi-tab browsing, no per-tab renderer processes, no WebGL or WebGPU, no embedded PDF viewer, and no AI-style web APIs.
Video is MPEG-1 only: there is no MPEG-4 or H.264 decoder and no Media Source Extensions, so streaming video sites do not play. Web Audio renders mono, and AudioParam automation curves are ignored. The stop button ends the loading state and marks the frame stale, but does not abort the network request behind it.
Where the engine stands against the HTML and CSS specifications — per-area web-platform-tests scores, how to reproduce them, and the known structural gaps — is recorded in docs/compliance.md.
specifications
| version | 1.0.6 — released 31 July 2026 · announcement |
|---|---|
| character | free-software edition of the Nordstjernen project · single window, single page, single process |
| language | C · ~149 kLOC original, excluding the vendored WAMR, Wuffs and audio decoders · GTK 4 shell · fully auditable |
| html / css | lexbor v3.0.0 (parser, WHATWG URL, selectors) · the engine's own cascade and layout |
| javascript | quickjs-ng v0.15.1 — bytecode interpreter, no JIT |
| text | ns-pango — a Pango fork with a process-wide shaping cache · HarfBuzz · FriBidi |
| webassembly | WAMR (vendored subset) — interpreter behind the WebAssembly JS API |
| images | Wuffs v0.4 (PNG / APNG / GIF / BMP / JPEG / WebP) · AVIF via libavif (optional) · SVG rendered in-engine |
| media | MPEG-1 <video> via pl_mpeg, with play, pause and seeking · audio — MP3, MP2, Ogg Opus/Vorbis · Web Audio graph · no H.264 and no Media Source Extensions |
| extensions | WebExtensions — local extensions with content scripts, packaged resources, storage and runtime messaging |
| webgl | — (no WebGL, no WebGPU) |
| ai | none — no AI assistant and no AI-style web APIs, by design |
| ui | GTK 4 (≥ 4.14; ≥ 4.22.1 on Windows) · dark theme follows the desktop |
| network | libcurl ≥ 8.5 · HTTP/2 · HTTP/3 through the alt-svc cache when the linked libcurl provides it · request deduplication and reusable preloads · Vary-aware caching |
| hardening | Landlock filesystem sandbox + PR_SET_NO_NEW_PRIVS · default-deny seccomp filter on Linux, in GUI and headless modes · no JIT |
| privacy | no telemetry · no update pings · HSTS · CSP · SRI · partitioned cookies and storage · on-device safe browsing against a local blocklist |
| standards | behaviour measured against the spec text, section by section · web-platform-tests run through headless mode · see docs/compliance.md |
| platforms | linux (primary) · macos · windows |
| license | GNU GPL v3 or later — free software |
| source | github.com/nordstjernen-web/northstar-browser |
See the side-by-side comparison of Nordstjernen and Northstar on the home page.
download
Latest tagged release: Northstar 1.0.6 — released 31 July 2026. full release notes »
| Windows | northstar-1.0.6-windows-x86_64.zip — self-contained, 57 MB compressed, 156 MB unpacked |
|---|---|
| Fedora (source RPM) | northstar-1.0.6-1.fc44.src.rpm |
| Linux & macOS | build from source with meson — see build and run below |
| Source | 1.0.6.tar.gz · 1.0.6.zip |
| All releases | github.com/nordstjernen-web/northstar-browser/releases |
The Windows build needs no installer and no MSYS2 — extract it anywhere and run
northstar.exe. Windows marks anything downloaded from the internet as
blocked, so before extracting, right-click the .zip, choose Properties,
tick Unblock at the bottom of the General tab and press OK. Doing it on the
archive first saves repeating it on northstar.exe afterwards, since the
mark is copied to every file extracted from a blocked archive.
build and run
Linux is the primary platform. On Debian or Ubuntu, install the development packages and build with meson:
| dependencies | 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 |
|---|---|
| build | meson setup builddir · meson compile -C builddir |
| run | ./builddir/src/gtk/northstar |
| smoke test | ./scripts/dev.sh build · ./scripts/dev.sh smoke — renders deterministic local fixtures through the headless engine and compares them with the checked-in baselines |
| headless | ./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; lexbor, quickjs-ng and ns-pango are
fetched by meson setup as pinned upstream subprojects. Full instructions are in
the README.
news
- · Northstar 1.0.6 released — a rebuilt grid, an indexed CSS cascade, faster text through ns-pango, Web Audio that renders, and relative colour syntax. Announcement » · Release notes »
- · Northstar 1.0.5 released — in-engine SVG, WebP/APNG, MPEG-1 video playback, and much better HTML, CSS and JavaScript compatibility. Announcement » · Release notes »
- · Northstar 1.0.4 released — a maintenance release. Release notes »
- · Northstar 1.0.3 released — Media Queries Level 4, CSSOM used values, and use-after-free fixes. Announcement » · Release notes »
- · Northstar 1.0.2 released. Release notes »
- · Northstar 1.0.1 released — the first public release of the GPL edition. Release notes »