Byline:

A fast, global content delivery network for ES Modules. All modules are transformed to ESM by esbuild in NPM.

Key links

“A New-Age CDN for JavaScript modules. Load modern JavaScript packages built for you on-demand. Works in modern web browsers, node.js, and deno.”

Supports ES Modules i.e. import rather than require. It appears that the service converts packages in the old format to be available with the new format.

The name of the site of course reflects ES Modules aka ESM.

URL format: https://esm.run/PACKAGE

e.g. https://esm.run/d3 redirects to https://cdn.jsdelivr.net/npm/d3/+esm.

The result says it was bundled with Rollup and Terser.