A WebAssembly plugin.

Typst is capable of interfacing with plugins compiled to WebAssembly. Plugin functions may accept multiple byte buffers as arguments and return a single byte buffer. They should typically be wrapped in idiomatic Typst functions that perform the necessary conversions between native Typst types and bytes.

Plugins run in isolation from your system, which means that printing, reading files, or anything like that will not be supported for security reasons. To run as a plugin, a program needs to be compiled to a 32-bit shared WebAssembly library. Many compilers will use the WASI ABI by default or as their only option (e.g. emscripten), which allows printing, reading files, etc. This ABI will not directly work with Typst. You will either need to compile to a different target or stub all functions.

Plugins and Packages

Plugins are distributed as packages. A package can make use of a plugin simply by including a WebAssembly file and loading it. Because the byte-based plugin interface is quite low-level, plugins are typically exposed through wrapper functions, that also live in the same package.


Plugin functions must be pure: Given the same arguments, they must always return the same value. The reason for this is that Typst functions must be pure (which is quite fundamental to the language design) and, since Typst function can call plugin functions, this requirement is inherited. In particular, if a plugin function is called twice with the same arguments, Typst might cache the results and call your function only once.


#let myplugin = plugin("hello.wasm")
#let concat(a, b) = str(

#concat("hello", "world")


To be used as a plugin, a WebAssembly module must conform to the following protocol:


A plugin module can export functions to make them callable from Typst. To conform to the protocol, an exported function should:


Plugin modules need to import two functions that are provided by the runtime. (Types and functions are described using WAT syntax.)


For more resources, check out the wasm-minimal-protocol repository. It contains:

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Creates a new plugin from a WebAssembly file.

plugin() -> plugin

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Path to a WebAssembly file.