Owi serves as an interpreter and toolkit tailored for WebAssembly (Wasm), in particular it can perform symbolic program execution. It builds upon techniques from the WASP engine but offers significant advantages in speed and maintenance. Its distinctive design employs a higher-order module with parameterization, facilitating efficient code sharing between concrete and symbolic interpreters. This is achieved without incurring abstraction costs, thanks to the OCaml compiler and the rights inlining annotations. Additionally, Owi harnesses OCaml multicore for parallel symbolic execution, further enhancing its performance and scalability in Wasm program analysis. Notably, Owi is capable of executing C programs compiled to Wasm with the owic front-end.