What is WebAssembly? A New Standard for Web Development

What is WebAssembly? A New Standard for Web Development
Photo by Alexander Sinn / Unsplash

WebAssembly, or Wasm for short, is a binary instruction format that can run on web browsers. It is designed to be fast, portable, and secure. Wasm aims to provide a common target for compiling high-level languages such as C, C++, Rust, and Go, and enable them to run on the web with near-native performance.

History of WebAssembly

The idea of running compiled code on the web is not new. In fact, there have been several attempts to achieve this goal in the past, such as Java applets, ActiveX, Flash, and Silverlight. However, these technologies had various drawbacks, such as security issues, browser compatibility problems, and poor performance.

The first prototype of WebAssembly was created in 2015 by a team of engineers from Mozilla, Google, Microsoft, and Apple. They wanted to create a low-level, efficient, and cross-platform format that could leverage the existing web platform and JavaScript engine. They also wanted to make it easy to interoperate with JavaScript and the web APIs.

The first version of WebAssembly was officially released in 2017, and since then, it has been supported by all major browsers. The Web Assembly Community Group and the Web Assembly Working Group are responsible for developing and standardizing the specification and features of Web Assembly.

Why Web Assembly was needed

WebAssembly was needed for several reasons. One of them was to enable developers to use their preferred languages and tools to create web applications, without being limited by the capabilities and performance of JavaScript. Another reason was to improve the user experience and performance of web applications, especially for computationally intensive tasks such as graphics, games, and multimedia. A third reason was to provide a consistent and secure execution environment for web applications, regardless of the underlying hardware and operating system.

Predecessors of WebAssembly

One of the predecessors of Web Assembly was asm.js, a subset of JavaScript that was optimized for performance. asm.js was introduced by Mozilla in 2013, and it allowed developers to compile C and C++ code to JavaScript that could run faster on browsers. asm.js was also compatible with existing web technologies and could fall back to normal JavaScript if the browser did not support it.

Another predecessor of Web Assembly was Emscripten, a tool that could compile C and C++ code to asm.js or Web Assembly. Emscripten was also developed by Mozilla, and it provided a comprehensive set of libraries and APIs to emulate the functionality of native code on the web. Emscripten was used to port many applications and games to the web, such as Unreal Engine, Unity, and Doom.

Benefits of WebAssembly

Web Assembly has many benefits for web development. Some of them are:

  • Performance: Web Assembly can run faster than JavaScript, as it is closer to the native machine code and can take advantage of the browser’s optimization techniques. Web Assembly can also reduce the loading time and bandwidth usage of web applications, as it is more compact and efficient than JavaScript.
  • Portability: Web Assembly can run on any web browser, regardless of the operating system and hardware. Web Assembly can also run outside the browser, on platforms such as Node.js, Electron, and WebAssembly System Interface (WASI).
  • Security: Web Assembly is designed to be safe and sandboxed, meaning that it cannot access the memory or resources of the host system without explicit permission. Web Assembly also enforces strict type and memory checks, preventing common errors and vulnerabilities.
  • Interoperability: Web Assembly can easily interact with JavaScript and the web APIs, using features such as JavaScript bindings, import and export of functions and values, and shared memory and threads. Web Assembly can also integrate with other web technologies, such as WebAssembly Modules, WebAssembly Interface Types, and Web Components.

Features of WebAssembly

Web Assembly has many features that make it a powerful and flexible format for web development. Some of them are:

  • Binary format: Web Assembly is encoded in a binary format, which makes it compact, fast, and easy to parse and validate. Web Assembly also has a text format, which is a human-readable representation of the binary format, and can be used for debugging and testing purposes.
  • Instruction set: Web Assembly has a simple and uniform instruction set, which consists of basic operations such as arithmetic, logic, control flow, memory access, and function calls. Web Assembly also supports advanced features such as floating-point arithmetic, SIMD instructions, and exception handling.
  • Module structure: Web Assembly is organized in modules, which are self-contained units of code that can be loaded and executed by the browser. Modules can define functions, variables, constants, tables, and memories, and can import and export them to other modules or the host environment. Modules can also be nested and composed to form larger applications.
  • Memory model: Web Assembly has a linear memory model, which is a contiguous and resizable array of bytes that can be accessed and manipulated by the module. Memory can be shared between multiple modules and threads, enabling parallel and concurrent programming. Memory can also be initialized and manipulated by using data and element segments, which are chunks of data that can be copied to or from the memory.
  • Type system: Web Assembly has a static and strong type system, which ensures that the code is valid and consistent. Web Assembly supports four basic value types: 32-bit and 64-bit integers, and 32-bit and 64-bit floating-point numbers. Web Assembly also supports compound types, such as function types, reference types, and struct and array types.

Applications of WebAssembly

Web Assembly has many applications and use cases for web development. Some of them are:

  • Games: Web Assembly can enable high-performance and immersive games on the web, using frameworks such as Unreal Engine, Unity, and Godot. Web Assembly can also leverage web technologies such as WebGL, WebXR, and Web Audio to provide rich graphics, sound, and interaction.
  • Media: Web Assembly can enable fast and efficient processing and encoding of media formats on the web, such as images, video, and audio. Web Assembly can also support new and emerging media standards, such as AV1, WebM, and WebP.
  • Machine learning: Web Assembly can enable machine learning and artificial intelligence on the web, using libraries such as TensorFlow, PyTorch, and ONNX. Web Assembly can also take advantage of hardware acceleration and parallelism, such as WebGPU, WebNN, and WebAssembly Threads.
  • Desktop applications: Web Assembly can enable desktop applications to run on the web, using platforms such as Electron, Blazor, and Flutter. Web Assembly can also provide native-like features and performance, such as file system access, networking, and cryptography.

Challenges of WebAssembly

WebAssembly is a promising technology that has many advantages for web development, but it also faces some challenges that limit its adoption and usability. Some of these challenges are:

  • Debugging and troubleshooting: WebAssembly modules are compiled to binary format, which makes them difficult to debug and inspect. Although there are some tools and techniques that can help with debugging, such as source maps, breakpoints, and stack traces, they are not widely supported or standardized across different browsers and runtimes. Moreover, WebAssembly does not have a built-in exception handling mechanism, which means that errors and crashes can be hard to detect and recover from12.
  • Performance variability: WebAssembly modules can run faster than JavaScript, but their performance can vary depending on the browser, runtime, and hardware. For example, some browsers may have faster or slower WebAssembly engines, some runtimes may have different optimization levels or garbage collection strategies, and some hardware may have different CPU architectures or memory models. These factors can affect the execution speed, memory usage, and power consumption of WebAssembly modules13.
  • Developer experience: WebAssembly modules can be written in different languages, such as C, C++, Rust, and Go, but they do not have a consistent developer experience across them. For instance, some languages may have better tooling, documentation, and community support than others, some languages may have more or less compatibility with WebAssembly features and APIs, and some languages may have different idioms and best practices than others. These differences can make it challenging for developers to learn, use, and collaborate with WebAssembly modules14.
  • Learning materials: WebAssembly is a relatively new and evolving technology, which means that there are not many learning materials available for it. Although there are some tutorials, books, and courses that can teach the basics of WebAssembly, they may not cover the latest features, standards, and proposals of WebAssembly. Moreover, there are not many examples, case studies, and benchmarks that can demonstrate the real-world applications, benefits, and challenges of WebAssembly15.
  • Browser compatibility: WebAssembly is supported by all major browsers, but there may be some compatibility issues with certain browsers or features. For example, some browsers may not support some WebAssembly features, such as threads, SIMD, or reference types, some browsers may have different security policies or restrictions for WebAssembly modules, and some browsers may have bugs or inconsistencies in their WebAssembly implementations. These issues can affect the functionality, reliability, and portability of WebAssembly modules1 .

These are some of the main challenges that WebAssembly faces today, but they are not insurmountable. The WebAssembly community and the industry are working hard to address these challenges and improve the technology. WebAssembly is still a young and growing technology, and it has a bright future ahead.

Future of WebAssembly

WebAssembly is a rapidly evolving and expanding technology, with many new features and proposals in the pipeline. Some of them are:

  • Garbage collection: Web Assembly will support garbage collection, which will enable languages such as Java, C#, and Python to run on Web Assembly without requiring manual memory management or external libraries.
  • Tail calls: Web Assembly will support tail calls, which will enable languages such as Scheme, Haskell, and Erlang to run on Web Assembly without requiring stack manipulation or trampolines.
  • Interface types: Web Assembly will support interface types, which will enable Web Assembly modules to communicate with each other and the host environment without requiring serialization or conversion of complex data structures.
  • Module linking: Web Assembly will support module linking, which will enable Web Assembly modules to dynamically link and load other modules at runtime, without requiring a central registry or a fixed layout.

WebAssembly is a revolutionary technology that has the potential to transform the web development landscape. It is a fast, portable, secure, and interoperable format that can run on any web browser and platform. It is also a flexible and extensible format that can support a wide range of languages, tools, and applications. Web Assembly is the future of web development.


WebAssembly is a game-changer for web development. It enables developers to use their favorite languages and tools to create web applications that are fast, portable, secure, and interoperable. It also opens up new possibilities and opportunities for web applications that were previously impossible or impractical. WebAssembly is not a replacement for JavaScript, but a complement that can enhance and enrich the web platform. Web Assembly is the web’s assembly language, and it is here to stay.