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Technical details

Technical details

This page summarizes some of the technical details for people familiar with the WASM ecosystem.


Golem uses a forked version of Wasmtime v17.0 (opens in a new tab). The fork contains minimal changes to the original required for implementing the durability properties of Golem. The forked repository is available on GitHub (opens in a new tab).


Golem provides the following host interfaces:

The WASI TCP and UDP interfaces are currently not supporting persistent execution but they are added to the linker to avoid linker errors for example with componentize-py outputs.

Component model, tiers, commands, reactors

Golem is built on the WebAssembly Component Model (opens in a new tab) from scratch. The components for Golem workers are WASM components, and the exported component model functions and instances are directly exposed via Golem's worker API for invocation.

As explained on the building components page, Golem uses the concept of tiers to categorize support for various guest languages.

The tiers are:

  • Tier 1 languages are having a WIT binding generator or directly support the component model and thus can be used to implement "reactor" (or "library") components, with multiple exported functions, and they can import and use any of the supported host interfaces.
  • Tier 2 languages have no binding generators, but they can be used with the preview1 adapter to implement "command" components, exposing a single parameterless run function. There are Golem features allowing some level of interactivity with these components via standard input and output.
  • Tier 3 languages are everything else


We have the following open-source repositories: