JSPM

JSPM is an open-source project for managing browser dependencies through import maps. Its CLI is the main command-line tool for import-map package management, while the jspm.io CDN loads optimized npm dependencies without a separate build step. The development server can install packages automatically, hot-reload, and strip TypeScript types. For production, jspm build uses RollupJS to bundle package entry points and dependencies. JSPM supports native ES modules, browser import maps, and standards-based workflows, and can add Subresource Integrity hashes across static and dynamic module graphs. Built-in providers include jspm.io, nodemodules, esm.sh, unpkg, skypack, and jsdelivr; custom providers can also be configured. Integrations include an online generator, VSCode web extension, Vite plugin, experimental Node.js loader, Import Map Rails, and Symfony AssetMapper. The hosted API generates import maps and dependency graphs, though JSPM recommends using its Generator library directly when possible. Import maps are supported in current Firefox, Safari, and Chrome versions, as well as Deno. The project is free and open source; its publish command is experimental and carries no reliability guarantees for jspm.io publishing.

JSPM provides tools for import-map workflows from development through production builds, alongside a CDN and hosted API. Treat its publishing command as experimental rather than a dependable publishing route.

JSPM is for developers managing browser dependencies with import maps and native ES modules. Its CLI, development server, build tool, and provider options cover development and production workflows.

Overview

JSPM is an open-source dependency manager built for browser import maps, with a command-line tool, CDN and hosted API. It is best suited to developers building with native browser modules who want a path from direct dependency imports to production bundles. The breadth of that workflow is compelling; package publishing through jspm.io is not a dependable production route.

Key features

The JSPM CLI is the primary tool for managing import maps. The jspm.io CDN loads optimized npm dependencies directly, avoiding a separate build step when that suits an application. Support for Node.js package exports, conditional exports and CommonJS-to-ES-module conversion makes more of the npm ecosystem usable in browser projects. RollupJS code-splitting optimization and source maps add useful production tooling to the CDN workflow.

For local development, jspm serve can install dependencies automatically, hot reload changes and strip TypeScript types. When a deployment needs bundles, jspm build uses RollupJS to bundle package entry points and dependencies. That flexibility is a practical advantage: teams can use native imports during development without being locked out of optimized production output.

JSPM can add Subresource Integrity hashes across an application's static and dynamic module graph, an option for projects that need integrity checks on loaded modules. The hosted API generates import maps and can return static and dynamic dependency graphs for preload generation. JSPM recommends running its Generator library directly where possible, making the hosted API a convenience for environments that cannot readily run JavaScript.

Projects can choose among jspm.io, nodemodules, esm.sh, unpkg, skypack and jsdelivr providers by default, or configure a custom provider. Official integrations include an online generator, a VSCode web extension, a Vite plugin, an experimental Node.js loader, Import Map Rails and Symfony AssetMapper. The range is useful across varied setups, though the Node.js loader is explicitly experimental.

The jspm.io CDN reports 99.99% historical uptime and describes redundant storage and caching layers. That is a favorable availability record, not a guarantee of future uptime. Compatibility is strongest in current environments: import maps are supported in the latest Firefox, Safari and Chrome versions, as well as Deno.

Pricing

JSPM is open source and free. The JSPM (open-source project) plan costs nothing and includes open-source import-map package management tools; jspm.io CDN services are also described as free and donation-supported. No paid tier or usage quota is stated for this plan. JSPM is funded by donations and sponsorships through the JSPM Foundation, a member-run Canadian not-for-profit corporation, so users relying on its hosted services should understand that their server costs are funded this way.

The project supports workspaces, lockfiles, peer dependency handling, package publishing, an offline package cache and global installation. These capabilities make it a more complete package-management workflow than a browser-import-only tool, but the publishing command is a significant exception: jspm publish is experimental, intended for prototyping and carries no reliability guarantees for publishing on jspm.io. Do not make it the release path for packages that need dependable publishing. Questions and discussion are directed to JSPM's Discord; priority support is listed as a sponsor benefit through Open Collective.

Platforms

JSPM lists support for API, extension, Linux, macOS, self-hosted use, web and Windows. Its browser import-map approach depends on compatible runtimes: current Firefox, Safari and Chrome, and Deno, support import maps.

Who it's for

JSPM is a strong fit for developers who want to manage dependencies around native browser modules, need to move between direct imports and RollupJS production bundles, or value provider choice and Subresource Integrity support. It is less suitable as a package-publishing foundation, and projects outside the supported import-map environments should not assume the browser workflow will fit.

Pros and cons

• Pros: Direct CDN imports can avoid a separate build step, while jspm build still provides a bundled production route.
• Pros: Support for Node.js exports, conditional exports and CommonJS conversion broadens npm package compatibility in browser projects.
• Pros: Provider choice, configurable custom providers and integrations such as the Vite plugin accommodate different project setups.
• Pros: The project combines free, open-source tools with an offline package cache, lockfiles and workspace support.
• Cons: jspm publish is experimental and explicitly lacks reliability guarantees, so it is unsuitable as a dependable publishing route.
• Cons: Import-map compatibility is tied to current Firefox, Safari and Chrome, or Deno, limiting the workflow where runtimes do not support the standard.
• Cons: The hosted CDN is donation-supported, and its reported historical uptime is not a future availability guarantee.

Alternatives

For a broader JavaScript package-manager choice, see JavaScript Package Managers.

• pnpm is a free alternative for readers who want a package manager on Android, Linux, macOS or Windows.
• Deno Sandbox is worth considering when the need is a hosted API or web sandbox: its free plan includes 1M requests/month and 10 hr active CPU, but excludes the Sandbox.
• npm is a fit for public package authors who want public registry access and unlimited public packages on its free plan.
• vlt offers a free web and self-hosted option with 2GB Storage+Delivery, upstream proxy, user and token management, and community support.
• Bun is an open-source, MIT-licensed JavaScript runtime and toolkit for readers seeking that kind of tool rather than JSPM's import-map workflow.
• Pantry is another free option for readers who want public packages, 30 days of full analytics, 50MB artifacts and a standard build queue.
• Textadept is a free, MIT-licensed text editor, not an import-map package manager.
• Yarn is a free open-source package manager with no paid plans or usage limits stated.

Verdict

Choose JSPM if you build browser applications around native ES modules and want import-map management, direct CDN delivery and a bundled production option in one free, open-source project. Its combination of provider flexibility and development-to-production tooling is the main reason to choose it. Look elsewhere if dependable package publishing is central to your workflow: JSPM's publish command is experimental, with no reliability guarantees.