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.WAT file extension

To open .WAT files on Windows, open the .wat file in a code editor (for example, Visual Studio Code) since it is plain text.

To open a .wat file, use a text editor or IDE (it’s plain text WebAssembly code). If you need to run it in a WebAssembly environment, first convert the .wat file to a .wasm binary with a tool like wat2wasm (WABT).

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Last updated: June 12, 2026

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .WAT files

Use these platform-specific instructions to open .WAT files safely.

Windows

  1. Open the .wat file in a code editor (for example, Visual Studio Code) since it is plain text.
  2. If you need a runnable module, convert it to .wasm using a WebAssembly tool such as WABT’s wat2wasm.
Full Windows guide

Mac

  1. Open the .wat file in a text editor or IDE (for example, Visual Studio Code) to view and edit the code.
  2. To execute it as WebAssembly, convert .wat to .wasm using a tool such as WABT’s wat2wasm.
Full Mac guide

Linux

  1. Open the .wat file in a text editor/IDE (for example, VS Code or a terminal editor) to inspect the text format.
  2. Convert it to .wasm with a tool such as WABT wat2wasm when you need the binary module.
Full Linux guide

iOS

  1. iOS does not commonly provide WebAssembly toolchains; view the file as plain text in a text editor app, or transfer it to a desktop to convert it to .wasm.
Full iOS guide

Android

  1. Open the file with a text editor app to view it as plain text, or move it to a desktop machine for conversion to .wasm using WebAssembly tools.
Full Android guide

Security notes

  • .wat is human-readable source text, but it can describe a module that, once converted to .wasm and executed, performs potentially unsafe or unexpected computations within the limits of the runtime environment.
  • Be cautious when running .wasm produced from untrusted .wat; treat it like running code obtained from the internet.
  • Some tools that parse/convert WebAssembly text are complex; only use reputable tooling when converting untrusted files.

Before you run downloaded code

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Can't open this file?

These are the most common causes and fixes when .WAT files fail to open.

Common reasons

  • The file opens as unreadable or with the wrong app
  • “It won’t run” because WAT is not the executable WebAssembly format
  • Conversion fails with parse/validation errors

Fix steps

  1. Open it explicitly in a code editor (e.g., VS Code) using File → Open.
  2. If needed, change the default app for .wat files to your preferred editor.

OS-specific troubleshooting

What is a .WAT file?

WAT is WebAssembly’s textual representation of a module, commonly saved with the .wat extension. It is designed to be readable and writable by humans, while the equivalent execution format is the binary WebAssembly module stored as .wasm. Tooling can translate between .wat and .wasm.

Background

WebAssembly has two common representations: a compact binary format used for execution (.wasm) and a human-readable text format often used for debugging, learning, or writing small modules by hand (.wat). The WebAssembly specification recommends “.wat” as the file extension for text-format modules.

Further reading

Authoritative resources for more details on the .WAT format.

Common .WAT issues

The file opens as unreadable or with the wrong app

.wat files are plain text, but the OS may associate the extension with an unrelated program or a non-text viewer.

  1. Open it explicitly in a code editor (e.g., VS Code) using File → Open.
  2. If needed, change the default app for .wat files to your preferred editor.

“It won’t run” because WAT is not the executable WebAssembly format

Browsers and runtimes typically load WebAssembly in the binary .wasm format; .wat is the text form used for authoring and inspection.

  1. Convert the .wat file to .wasm using wat2wasm (WABT) or equivalent tooling.
  2. Use the produced .wasm file in your WebAssembly workflow (for example, in a web project).

Conversion fails with parse/validation errors

wat-to-wasm conversion tools will reject WAT that does not match the expected text-format conventions or contains syntax errors.

  1. Check the file against WebAssembly text-format conventions and correct syntax issues.
  2. Try converting again with wat2wasm and fix the reported line/column errors.

FAQ

Is a .wat file the same as a .wasm file?

No. .wat is the human-readable WebAssembly text format, while .wasm is the binary format typically used for execution.

How do I convert .wat to .wasm?

Use a WebAssembly tool that supports converting text to binary, such as WABT’s wat2wasm (available as a demo and as tooling). MDN also documents the conversion workflow.

Does .wat have an official recommended extension?

Yes. The WebAssembly specification’s conventions recommend “.wat” for text-format WebAssembly modules.

Is there a registered MIME type specifically for .wat?

This depends on what is registered with IANA. If you need a standards-based media type, check the IANA Media Types registry for any current registration related to WebAssembly or a dedicated type for WAT.

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