Compute astrology charts in the browser: no node-gyp, no .se1 files, no AGPL

If you've wired Swiss Ephemeris into a Node astrology app, you know the ritual. You npm install sweph , and now every machine needs Python plus a C/C++ toolchain, because the package compiles Swiss's C code via node-gyp at install time (make/gcc on Linux, Xcode on macOS, Visual C++ Build Tools on Windows). It works on your laptop. Then it explodes: Apple Silicon: node-gyp can't find full Xcode behind Command Line Tools. Slim Docker / CI images: no Python, no build-essential , so the install dies. Serverless: the .node binary you built locally won't load on Amazon Linux (wrong arch or glibc). Then there's the data. Neither sweph nor swisseph bundles the .se1 ephemeris files; you download them yourself and point the library at a path. The modern set is 2 MB, the full GitHub set is 100 MB. And since 2.10.1 , sweph is AGPL-3.0 (LGPL only under a professional license), a real obligation to weigh for a closed-source SaaS backend. The pure-Rust alternative XALEN Ephemeris is an analytical engine written entirely in Rust and licensed Apache-2.0. Three things make it interesting for JS/TS devs: No node-gyp. The Node addon is napi-rs, which ships prebuilt per-platform binaries via npm. No Python, no C compiler, no compile step. A real WASM build via wasm-bindgen, so you compute charts client-side in the browser: no server round-trip, no backend copyleft. Zero data files. The core math (VSOP87A, ELP2000-82, IAU precession/nutation, an 8,870-star catalog) is analytical and compiled into the binary. No .se1 to host. import init , * as xalen from " xalen-ephemeris " ; // WASM build, runs in the browser await init (); // load the .wasm module const chart = xalen . computeChart ({ datetime : " 1990-04-12T08:30:00Z " , lat : 28.6 , lon : 77.2 }); console . log ( chart ); // planet longitudes, house cusps, etc. Swiss via Node XALEN (pure Rust) Build deps node-gyp + Python + C compiler none: prebuilt binary / .wasm Runtime data .se1 files (2 to 100 MB) none, compiled in Browser / WASM