Optimizing bundle size of Elm programs

Elm is well known for generating small bundle sizes (screenshot), as explained on the official website.

But after seeing this post about minifying Elm code I also wanted to investigate if the same results hold true when using the compiled Elm bundle as an ES module instead of the default IIFE output.

I want to use ESM, because I also load other parts of my applications in that format and I want to avaoid a global Elm state.

I have reached pretty much the same conclusion as Simon Lydell already published on the Elm discourse

• For the smallest file size using a single tool, you can either pick UglifyJS or Google's closure compiler. Both take about the same time (9.5-10s in my case).
• But you can achieve the same size result by running just parts of UglifyJS and then esbuild in about 40% of the time (~3.5s).
• Esbuild alone produces about 10% more code than UglifyJS, but it needs only ~2% of the time (0.1s) when directly writing to a file.
• SWC is comparable to Esbuild in compilation time, but not yet in compression ratio (16% bigger). They are working on reaching parity to terser, so re-visiting that in the future will be interesting.
• Terser produces ~4% more code than UglifyJS but only needs 60% of the time.

Full results are documented on this page.