Extism is a lightweight framework for building with WebAssembly (Wasm). It supports running Wasm code on servers, the edge, CLIs, IoT, browsers and everything in between. Extism is designed to be "universal" in that it supports a common interface, no matter where it runs.
Note: One of the primary use cases for Extism is building extensible software & plugins. You want to be able to execute arbitrary, untrusted code from your users? Extism makes this safe and practical to do.
Additionally, Extism adds some extra utilities on top of standard Wasm runtimes. For example, we support persistent memory/module-scope variables, secure & host-controlled HTTP without WASI, runtime limiters & timers, simpler host function linking, and more. Extism users build:
- plug-in systems
- FaaS platforms
- code generators
- web applications
- & much more...
Pick a SDK to import into your program, and refer to the documentation to get started:
| Type | Language | Source Code | Package |
|---|---|---|---|
| Rust SDK |  |
https://github.com/extism/extism/tree/main/runtime | Crates.io |
| JS SDK |  |
https://github.com/extism/js-sdk (supports Web, Node, Deno & Bun!) |
NPM |
| Elixir SDK |  |
https://github.com/extism/elixir-sdk | Hex |
| Go SDK |  |
https://github.com/extism/go-sdk | Go mod |
| Haskell SDK |  |
https://github.com/extism/haskell-sdk | Hackage |
| Java SDK |  |
https://github.com/extism/java-sdk | Sonatype |
| .NET SDK |  |
https://github.com/extism/dotnet-sdk (supports C# & F#!) |
Nuget |
| OCaml SDK |  |
https://github.com/extism/ocaml-sdk | opam |
| Perl SDK |  |
https://github.com/extism/perl-sdk | CPAN |
| PHP SDK |  |
https://github.com/extism/php-sdk | Packagist |
| Python SDK |  |
https://github.com/extism/python-sdk | PyPi |
| Ruby SDK |  |
https://github.com/extism/ruby-sdk | RubyGems |
| Zig SDK |  |
https://github.com/extism/zig-sdk | N/A |
| C SDK |  |
https://github.com/extism/extism/tree/main/libextism | N/A |
| C++ SDK |  |
https://github.com/extism/cpp-sdk | N/A |
Extism Hosts (running the SDK) must execute WebAssembly code that has a PDK, or Plug-in Development Kit,
library compiled in to the .wasm binary. PDKs make it easy for plug-in /
extension code authors to read input from the host and return data back, read
provided configuration, set/get variables, make outbound HTTP calls if allowed,
and more.
Pick a PDK to import into your Wasm program, and refer to the documentation to get started:
| Type | Language | Source Code | Package |
|---|---|---|---|
| Rust PDK | |
https://github.com/extism/rust-pdk | Crates.io |
| JS PDK | |
https://github.com/extism/js-pdk | N/A |
| Go PDK | |
https://github.com/extism/go-pdk | Go mod |
| Haskell PDK | |
https://github.com/extism/haskell-pdk | Hackage |
| AssemblyScript PDK |  |
https://github.com/extism/assemblyscript-pdk | NPM |
| .NET PDK | |
https://github.com/extism/dotnet-pdk (supports C# & F#!) |
https://www.nuget.org/packages/Extism.Pdk |
| C PDK | |
https://github.com/extism/c-pdk | N/A |
| Zig PDK | |
https://github.com/extism/zig-pdk | N/A |
If you experience any problems or have any questions, please join our Discord and let us know. Our community is very responsive and happy to help get you started.
Head to the project website for more information and docs. Also, consider reading an overview of Extism and its goals & approach.
Thank you for considering a contribution to Extism, we are happy to help you make a PR or find something to work on!
The easiest way to start would be to join the
Discord or open an issue on the
extism/proposals issue tracker, which
can eventually become an Extism Improvement Proposal (EIP).
For more information, please read the Contributing guide.
Extism is an open-source product from the team at:
Reach out and tell us what you're building! We'd love to help: [email protected]