Note: There was some discussion of Wasmer here a couple of days ago: https://news.ycombinator.com/item?id=30758651

Excellent, thank you! I knew of Wasmer but didn't realize that's what it was. I look forward to the day where we can just distribute one architecture-independent binary.

Like a .jar file?

Yes, but with a much leaner, memory-efficient, and more secure runtime. WASM is kinda "JVM without the Java bits" but that's a good thing. Having the VM provide facilities for GC is not necessary. Go shows that you can embed it in the executable. And Java bytecode is too close to Java code and not close enough to machine code, and so the VM has to provide a full interpreter - also unnecessary.

Wasm requires a full JS runtime no? At this point those are no lighter than a full JVM.

Nope! Much like Node allows you to run JavaScript without a browser, there are plenty of standalone WebAssembly runtimes which don't need a host JavaScript runtime.