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.WASM file extension

To open .WASM files on Windows, if you expect it to run as part of a website: open the site in a modern browser; the page’s JavaScript will load the .wasm module via the WebAssembly API.

To open a .wasm file, you usually load it as a WebAssembly module in a web page (through the WebAssembly APIs) or run it with a WebAssembly runtime outside the browser (for example, Wasmtime). Double-clicking a .wasm file normally won’t do anything useful because it’s a compiled binary module, not a document.

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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 .WASM files

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

Windows

  1. If you expect it to run as part of a website: open the site in a modern browser; the page’s JavaScript will load the .wasm module via the WebAssembly API.
  2. If you want to run it locally outside the browser: install a WebAssembly runtime such as Wasmtime, then run it from a terminal (for example, by invoking the runtime with the .wasm file).
  3. If you only need to inspect it: open it in a code editor or hex viewer to confirm it is a WebAssembly binary (it will be binary data, not readable source).
Full Windows guide

Mac

  1. If it belongs to a web app: open the associated web page in a modern browser; the .wasm file is fetched and executed by the WebAssembly Web API.
  2. To run it outside the web: install a WebAssembly runtime such as Wasmtime and run the module from Terminal using the runtime’s command.
  3. To inspect the file: open it with a code editor or binary viewer (it won’t display as human-readable text).
Full Mac guide

Linux

  1. If it’s part of a web project: open the related page/app in a modern browser; it will load the .wasm module through the WebAssembly APIs.
  2. To execute it directly: install a WebAssembly runtime such as Wasmtime and run the module from your shell using the runtime.
  3. For analysis: open it with a binary-capable editor/viewer to verify it is a WebAssembly module file.
Full Linux guide

iOS

  1. iOS does not typically “open” .wasm as a standalone file; if it is used, it’s usually loaded by a web page in a browser. For direct execution or deeper inspection, transfer the file to a desktop OS and use a WebAssembly runtime or developer tools.
Full iOS guide

Android

  1. Android does not commonly run .wasm as a standalone file; it is typically used by web apps in a mobile browser. For direct execution, move the file to a desktop OS and use a WebAssembly runtime such as Wasmtime.
Full Android guide

Security notes

  • .wasm is executable code in a sandboxed WebAssembly environment; treat untrusted .wasm like untrusted scripts—loading it in a web page or runtime can run attacker-controlled logic.
  • A .wasm module can still trigger security-relevant behavior through the host environment (imports and APIs provided by JavaScript or a runtime), so the effective risk depends on what capabilities the host gives it.
  • Because .wasm is a binary format, bugs in compilers, runtimes, or toolchains that parse/compile it can be a security risk; prefer well-maintained, standards-based implementations and keep runtimes/browsers updated.

If you did not expect this file

This extension is usually plain data, text, or structured content—not a program by itself. The practical risk is social engineering (a scam attachment or misleading filename). For trusted senders you rarely need heavy-handed antivirus wording; use these tools when you want an extra check on unexpected downloads.

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Can't open this file?

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

Common reasons

  • Double-clicking the file doesn’t open anything
  • It won’t run by itself (missing imports / needs JavaScript)
  • Web server serves the wrong content type for .wasm

Fix steps

  1. Determine whether the .wasm came from a web app; if so, open the corresponding page/project instead of the file by itself.
  2. If you need to run it locally, use a WebAssembly runtime (for example, Wasmtime) from a terminal.
  3. If you just need to view what it is, open it in a code editor or binary viewer to confirm it’s a WebAssembly binary module.

OS-specific troubleshooting

What is a .WASM file?

A .wasm file is a WebAssembly binary module. The WebAssembly core specification defines its binary encoding, including a module header and a sequence of sections. Browsers can fetch a “.wasm” resource via the WebAssembly Web API and then compile/instantiate it for execution.

Background

WebAssembly (often shortened to “Wasm”) is a portable, low-level code format intended for safe and efficient execution. The W3C announced the WebAssembly specifications as W3C Recommendations and notes that the WebAssembly Web API executes a “.wasm” resource in the web platform.

In practice, .wasm files are rarely used alone; they are commonly paired with JavaScript “glue” code that loads the module, supplies imports, and calls exported functions. This is why users often encounter .wasm as part of a website or web app’s assets rather than as a standalone file to open.

Outside the browser, .wasm modules can be executed by dedicated runtimes. For example, Wasmtime documentation describes running WebAssembly binaries (typically with the .wasm extension) as a way to use WebAssembly beyond the web.

Common MIME types: application/wasm

Further reading

Authoritative resources for more details on the .WASM format.

Common .WASM issues

Double-clicking the file doesn’t open anything

.wasm is a compiled binary module and usually needs a runtime (browser WebAssembly APIs or a standalone runtime) rather than a document viewer.

  1. Determine whether the .wasm came from a web app; if so, open the corresponding page/project instead of the file by itself.
  2. If you need to run it locally, use a WebAssembly runtime (for example, Wasmtime) from a terminal.
  3. If you just need to view what it is, open it in a code editor or binary viewer to confirm it’s a WebAssembly binary module.

It won’t run by itself (missing imports / needs JavaScript)

Many WebAssembly modules are designed to be instantiated with specific imports provided by JavaScript (or another host environment). Without the expected host functions and setup, instantiation or execution can fail.

  1. Look for companion files in the same project (often JavaScript that loads the .wasm module via WebAssembly APIs).
  2. Run it in the intended environment (e.g., the web app or the runtime/toolchain it came with) rather than treating it as a standalone executable.
  3. If using a standalone runtime, ensure you are invoking it in a way that matches the module’s expectations (exports/entry points and imports).

Web server serves the wrong content type for .wasm

When delivered over the web, a .wasm file should be served with the appropriate registered media type. Incorrect server configuration can cause loading/compilation issues in browsers.

  1. Check the server’s response headers for the .wasm request and verify the Content-Type is correct.
  2. Configure your web server to serve .wasm with the registered media type for WebAssembly.
  3. Use browser developer tools (Network tab) to confirm the .wasm resource is fetched with the expected headers.

FAQ

Is a .wasm file the same as JavaScript?

No. WebAssembly is a separate binary module format designed for efficient execution; it is often used alongside JavaScript, which typically loads and interacts with the .wasm module via WebAssembly APIs.

Can I open a .wasm file in a browser by clicking it?

Usually not in a meaningful way. Browsers execute .wasm when it is loaded by a web page using the WebAssembly Web API; the module is typically fetched as a resource and instantiated by JavaScript.

What is the official media type (MIME type) for .wasm?

The WebAssembly specification recommends a media type, and IANA is the authoritative registry for registered media types. In practice, configure servers according to the IANA registration and the WebAssembly spec guidance for serving WebAssembly binaries.

Can .wasm run outside the browser?

Yes. WebAssembly modules can be executed by standalone runtimes; for example, Wasmtime documentation describes running WebAssembly binaries (typically with the .wasm extension) outside the web.

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