We use tsup to build most packages. (The only exception for this is the @react-email/tailwind package which currently uses vite due to a few issues with tsup and tailwindcss’s bundling.) To build a package run:
package/* (ex: package/render)
pnpm build
Building in each package will run tsup with a few settings, typically src/index.ts --format esm,cjs --dts --external react. Tsup handles building both ESM and CJS versions along with the type definitions exported from the entry point, src/index.ts, without bundling react, which can cause issues.

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Why build before publishing?

We build most of the packages before publishing for a few reasons:
  1. All the exported types can be imported from the same place the JavaScript is imported
  2. We have proper CommonJS and ES Modules support
  3. Code that isn’t exported is not published or downloaded