I don't know about running them in a browser, but the related projects CakeML [1] and CompCert [2] are both pretty easy to download and run, and very featureful

I don't know about running them in a browser, but the related projects CakeML [1] and CompCert [2] are both pretty easy to download and run, and very featureful. [1] https://cakeml.org/ https://cakeml.org/ [2] http://compcert.inria.fr/compcert-C.html http://compcert.inria.fr/compcert-C.html