Modules

In WebAssembly, everything is organized into stateless objects called modules. The Wasm code that makes up a module is divided into multiple sequential sections. The code is compiled by the browser, and modules are instantiated through the WebAssembly.Module() method.

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Sections

The following table shows the known possible sections that can be part of a Wasm module:

name	contents
Code	Holds the body of every function listed in the Function section.
Data	Declares the data that will be loaded into the Memory section.
Function*	Lists all the functions in the module.
Global*	Defines global variables for the module.
Import*	Lists all the imports used by the module.
Element	Declares the data that will be loaded into the Table section.
Export*	Lists all the exports that will be exposed to the host environment from inside the module.
Memory*	Holds the linear memory used by an instance of the module.
Start	Declares the index of a function that is executed as a Wasm module is instantiated.
Table*	Holds a typed array of references to items that can’t be stored as raw bytes in linear memory.
Type	Lists all signatures for functions the module uses. A signature can be shared between functions.

* Shown in the WASM Analyzer interface.

In addition to the known sections listed above, a Wasm module may also contain one or more custom sections that add non-standard functionality. Custom sections must appear after the Data section in a module.

Read more about the contents of the various sections, and the building blocks of a module in the Building blocks section of this documentation.

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Additional reading

Read more about the contents of the various sections contained within a module in our documentation on WebAssembly building blocks, here.