The Wasmer WebAssembly runtime provides various features for users and developers:

• Compilers: Wasmer supports multiple compilers: Singlepass, Cranelift and LLVM. Each of these have different tradeoffs of compilation speed vs runtime speed;

• Caching: compiled WebAssembly modules can be reused so subsequent runs of a Wasm file will have very little start up time;

• Metering: computation time and other resources can be monitored and limits set to control how the Wasm code runs. This is also known as "gas metering";

• WebAssembly Features:

  • Bulk-memory operations: e.g. instructions with behavior similar to C's memmove and memset in WebAssembly;

  • Multi-value return: return multiple values from functions making data transfer between host and guest simpler;

  • Import & export of mutable globals: adds ability to import and export mutable globals;

  • Non-trapping float-to-int conversions: this proposal would establish a convention for saturating operations, to avoid introducing trapping;

  • Sign-extension operations: adds five new integer instructions for sign-extending 8-bit, 16-bit, and 32-bit values;

  • Reference types: easier and more efficient interop with host environment;

  • SIMD: Single Instruction, Multiple data: do heavy number crunching more quickly and/or with lower power usage.

  • Threads: adds a new shared linear memory type and some new operations for atomic memory access;

• ABIs: it allows running different types of programs compiled to WebAssembly, with ABIs such as:

  • Emscripten

  • WASI

Support of features by Compiler

Runtime features:

WebAssembly features:

Support by Operating System

* poll_fd is not fully implemented for Windows yet

Compiler Support by Chipset

Language Embeddings

Wasmer enables WebAssembly usage in a lot of different languages. Here are some of the features in each of those: