If you’ve ever wondered what WebAssembly (Wasm) is and how it fits into the service mesh ecosystem, this is the article you want to read. We’ll explain what Wasm can do and set the stage by talking a bit about extensibility in Envoy Proxy. Envoy is a service (sidecar) and edge proxy (gateway) that can be configured through APIs. Next we’ll talk about how Wasm fits into Envoy, covering WasmService and Proxy-Wasm. This article is written for Wasm beginners, and we assume you don’t have any in-depth Wasm knowledge. In a companion article, we’ll explore Wasm using Kubernetes and Istio so you can be comfortable using both. You can check out the Istio Fundamentals course to learn how to get started with Istio.