Northstar Browser

Northstar is a minimalist web browser written from scratch in C. One window, one page, one process — about 188,000 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 — on Windows from the Microsoft Store.

Northstar Browser version 1.0.20 released! Video is now decoded by the operating system by default — Media Foundation on Windows, GStreamer on Linux — fonts created with the FontFace API load, YouTube and Media Source fixes come over from Nordstjernen Sol, and security fixes cover module-import CORS, security headers on cached responses, HttpOnly cookies written from script and CSP sandboxing of frames. More info here.

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, transitions and @keyframes animations on every property (with a Web Animations API from script), gradients, border-image, container queries, scroll snap on scroll containers and on the page itself, relative colour syntax and the color() function across nine colour spaces.
• JavaScript. quickjs-ng, a bytecode interpreter with no JIT (or Fabrice Bellard’s original QuickJS, with -Djs_engine=quickjs) — DOM, Shadow DOM, observer APIs, Canvas 2D (Path2D, ImageBitmap, DOMMatrix) and WebCrypto (crypto.subtle over OpenSSL).
• Frames — a framed document gets its own realm and its own Content-Security-Policy, and cross-document postMessage works in both directions.
• 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, @page sheet sizes and margins, and the break-* properties all apply; --dump=print:FILE writes the same pagination to a multi-page PDF.
• Custom elements — autonomous and customized built-in elements, with the insertion steps that make connectedCallback fire 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/sessionStorage and 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, storage.local, i18n and declarativeNetRequest rule sets.
• 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, AAC, 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. Since 1.0.13 streaming sites play through Media Source Extensions: fragmented MP4 and WebM are demuxed in-tree, a decoder thread per video decodes AV1 (libdav1d), VP9 (libvpx) or H.264 (OpenH264, optional) a few frames ahead, and the sound decodes AAC-LC (in-tree) or Opus. A plain MP4 or WebM file in <video src> is fetched progressively with HTTP range requests and plays the same way, and controls draws a play/pause button, seek bar, time and mute button.
• WebAssembly — the JavaScript API over a vendored WAMR fast interpreter, with no JIT. MathML — a minimalist presentation-MathML renderer. Spell checking — optional, via Enchant.
• The browser itself — a classic labelled toolbar, an address bar that suggests from bookmarks and history as you type, 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 flagship multi-tab browser 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 codecs come from optional system libraries: without libdav1d, libvpx or OpenH264 at build time, the matching streams do not play, and a file that is none of the supported formats falls back to the MPEG-1 path. Only Cisco’s prebuilt OpenH264 binaries carry Cisco’s H.264 patent licence, so -Dh264=disabled drops H.264 where that matters.

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

See the side-by-side comparison of Nordstjernen and Northstar on the home page.

download

Latest release: Northstar 1.0.20 — released 1 November 2026, as source and on the Microsoft Store. full release notes »

The most recent prebuilt Linux and Windows zips are from Northstar 1.0.7 — released 8 August 2026. read the announcement » · full release notes »

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.

Download Northstar 1.0.20 »

build and run

Linux is the primary platform. On Debian or Ubuntu, install the development packages and build with meson:

Meson feature options include -Davif=disabled, -Daudio=disabled, -Dh264=disabled, -Dwasm=disabled and -Dgtk=disabled for smaller or engine-only builds. WAMR, Wuffs, pl_mpeg and minimp3 are vendored in-tree. lexbor and quickjs-ng take a system copy whenever the build finds one new enough and fall back to a pinned upstream subproject; ns-pango is always the subproject, because its renamed symbols are what let it sit beside the system Pango that GTK loads. Full instructions are in the README and docs/building.md.

news

• 1 NOV 2026 · Northstar 1.0.20 released — video decoded by Media Foundation on Windows and GStreamer on Linux by default, the FontFace API, YouTube and Media Source fixes, and security fixes. Release notes »
• 18 OCT 2026 · Northstar 1.0.15 released — no executable memory for the engine, a Landlock fix for ~/.Xauthority sessions, opaque file: origins, a live document.cookie, the browser named as itself in client hints, and about 3,800 lines of dead and duplicated code removed. Release notes »
• 18 OCT 2026 · Nordstjernen 1.0.33 and Southstar 1.0.0, the all-Rust version, released. More »
• 16 OCT 2026 · Northstar 1.0.14 released — video streaming fixes and security fixes from a source-wide review. Release notes »
• 9 OCT 2026 · Northstar 1.0.13 released — streaming video through Media Source Extensions and plain MP4 files (AV1, VP9 and H.264 with AAC or Opus), video decoding on its own thread, WAMR’s fast interpreter, Google Maps, XPath, and much cheaper restyling. Release notes »
• 5 OCT 2026 · Nordstjernen 1.0.29 released — sharp pages on HiDPI screens, smooth tiled scrolling, the clipboard in text fields, Google sign-in and a security audit of the engine. Announcement »
• 4 OCT 2026 · Nordstjernen 1.0.28 is now dual-licensed under the GNU GPL version 3 or later or the Nordstjernen Source License. Announcement »
• 2 OCT 2026 · Northstar 1.0.12 released — an 8 MB engine stack so deep pages no longer crash, and a build on Fabrice Bellard’s original QuickJS. Announcement » · Release notes »
• 27 SEP 2026 · Northstar 1.0.11 released — Northstar on the Microsoft Store. Release notes »
• 26 SEP 2026 · Northstar 1.0.10 released — text measurements that outlive relayout, partial repaint, an idle page that stays idle, popovers, grid fixes and canvas security. Announcement » · Release notes »
• 20 SEP 2026 · Northstar 1.0.9 released — a sunny ark comic on about:start, a Mozilla-style toolbar, address-bar suggestions, and a full-screen notice. Announcement » · Release notes »
• 16 SEP 2026 · Northstar 1.0.8 released — transitions and animations on every property with a Web Animations API, border-image, the background shorthand parsed layer by layer, position: fixed that stays put, flexbox and grid rebuilt against the specifications, and lexbor 3.0.1. Announcement » · Release notes »
• 6 SEP 2026 · CVE-2026-85046 and Northstar — the actively exploited Chrome V8 type confusion does not apply to Northstar or Nordstjernen: no V8, no JIT, no elements kind to confuse, no write barrier to skip. Read the analysis »
• 8 AUG 2026 · Northstar 1.0.7 released — printing through the system dialog, a rebuilt about:start sky and earth, CSS Scroll Snap, frames that reach their parent, quickjs-ng 0.16.1, and Linux binaries. Announcement » · Release notes »
• 31 JUL 2026 · 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 »
• 28 JUL 2026 · 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 »
• 23 JUL 2026 · Northstar 1.0.4 released — a maintenance release. Release notes »
• 22 JUL 2026 · Northstar 1.0.3 released — Media Queries Level 4, CSSOM used values, and use-after-free fixes. Announcement » · Release notes »
• 19 JUL 2026 · Northstar 1.0.2 released. Release notes »
• 18 JUL 2026 · Northstar 1.0.1 released — the first public release of the GPL edition. Release notes »

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