Providers

Provider	Build	Registries	Notes
`esmSh()`	`esm.sh`	npm, jsr, github	transforms to browser ESM; URLs carry `?target=es2022` (`esTarget`) so the bytes, and `integrity`, don’t vary by browser
`jsDelivr()`	`npm`	npm, github	raw files. The entry comes from `exports` → `module` → `main`, and sub-paths such as `preact/hooks` are mapped through `exports`
`jsDelivr({ esm: true })`	`jsdelivr-esm`	npm	jsDelivr’s `/+esm` bundles
`unpkg()`	`npm`	npm	raw files
`jspm()`	`jspm`	npm	`ga.jspm.io` builds
`jsr()`	`esm.sh`	jsr	through esm.sh. `jsr({ via: "jsr.io" })` loads raw files from jsr.io and needs a path
`github()`	`npm`	github	through jsDelivr’s `/gh/`. `{ via: "esm.sh" }` also works
`local({ base })`	`npm`	npm	your own copy, e.g. a vendored `node_modules`. It looks up versions and entries in the npm registry; for a package that is not on npm, or to serve the installed version, add `registry: installedRegistry({ root })` from `@johnhenry/mport/node` (below)
`custom(template)`	origin host	npm	`"https://x/"` or a template using `{name}` `{version}` `{path}` `{entry}` `{scope}` `{bare}`
`provider({...})`	yours	yours	write your own: `{ name, build, registries, capabilities, needsEntry, needsVersion, url(artifact) }`

Serving what is installed, including packages that are not on npm. local() maps to your own origin but still asks the registry for the version and entry file, so a package installed from git is a 404. @johnhenry/mport/node has a registry client that reads <root>/<name>/package.json instead:

import { createRouter, local } from "@johnhenry/mport";
import { installedRegistry } from "@johnhenry/mport/node";

const router = createRouter({ "*": local({ base: "/node_modules/" }) },
  { registry: installedRegistry({ root: "node_modules" }), probe: "none" });
await router.build(["@scope/unpublished"]);  // /node_modules/@scope/unpublished/<entry>, lock records the installed version

The installed version wins over the registry’s latest, and a range it does not satisfy is an error. See API › installedRegistry(); runnable: example 17.

The CDN providers (esmSh, jsDelivr, unpkg, jspm, jsr) accept origin, so you can point them at a self-hosted mirror. Full URL shapes and capabilities: API › Built-in providers.

CommonJS and raw CDNs. Raw file CDNs (jsDelivr(), unpkg(), jspm(), local()) serve files as published, so a package whose entry is CommonJS, such as React’s index.js, can’t be imported from them in a browser. mport skips those providers for such packages (skip with a reason) so the route falls through to an ESM-transforming CDN like esm.sh. ESM is detected from .mjs, an import/module export condition, the module field, "type": "module", or ESM-by-convention names (*.module.js, *.esm.js, …/esm/…). Pass createRouter(routes, { allowCommonJS: true }) to turn the check off. The exact rules: API › CommonJS detection.