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svelte-smol docs

A SvelteKit adapter that compiles your app to one standalone binary with Bun. No node_modules to ship, built-in healthcheck for Docker.

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Introduction

A SvelteKit adapter that compiles your app into a single standalone executable with bun build --compile. No nodemodules, no JS files to ship, just one binary plus its static assets.

Getting started

Install the adapter and ship your first binary.

Getting Started

Turn a SvelteKit app into a single standalone executable in a few minutes.

These are merged in before the adapter's own fields (fetch, idleTimeout, maxRequestBodySize, hostname/port/unix, websocket), so they can add to the server but not override request handling. Use the matching env vars (IDLETIMEOUT, BODYSIZELIMIT, HOST/PORT, SOCKETPATH) for those.

Running in production

Configure, deploy and put it behind a proxy.

Environment variables

Runtime settings are read from the environment when the executable starts — nothing is baked in at build time.

Deployment

Ship the whole build/ directory. With serveAssets: false, the executable alone is enough — a proxy or CDN serves client/ and prerendered/.

Health Check

With healthcheck on (the default) the build produces a second, tiny executable — build/healthcheck — and the server answers GET /health:

Reverse Proxy

Behind a proxy, the server sees the proxy's connection, not the browser's. Tell it where the real URL and client address come from.

Native Addons

Pure-JS dependencies are still bundled into index.js. A native addon's require stays in the output and resolves from nodemodules at runtime, looked up from index.js's own location — the working directory doesn't matter. A production install is enough:

Internals

How the code fits together.

Architecture

1. Writes client assets to out/client/ and prerendered pages to out/prerendered/ (compressing them if precompress is on). 2. Writes the SvelteKit server and a manifest.js into .svelte-kit/adapter-bun/. 3. Copies templates/ next to it, swapping the placeholder tokens — ENV, HANDLER, MANIFEST, SERVER become relative imports; ENVPREFIX, BUILDOPTIONS, SERVEOPTIONS become JSON literals. 4. Prepends import "./server/instrumentation.server.js" to the entrypoint if the app has one, so it loads before anything else. 5. Runs Bun.build on templates/index.ts — compile to a binary, or a plain index.js when compile: false — and compiles healthcheck.ts separately.