Welcome to SpiderMonkey

SpiderMonkey is Mozilla’s JavaScript and WebAssembly Engine, used in Firefox, Servo and various other projects. It is written in C++ and Rust.

What’s New

SpiderMonkey Internals

Building and Contributing

Embedding SpiderMonkey

Where to find us

NOTE: The mailing lists are being phased out. You can now connect to our Discourse category by email for a similar experience. The archives should continue to remain available at: