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Software Development / WebAssembly

What Is WebAssembly?

A primer on what developers need to know about WebAssembly, what it’s used for, its pros and cons, and what the future may hold for Wasm.
Sep 25th, 2023 4:00am by
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WebAssembly, or Wasm, is a cornerstone for many modern web-based applications. But what exactly is WebAssembly? Initially conceived to bring near-native performance to web applications, Wasm provides a compact binary format that serves as a compilation target for key programming languages like C++ and SQL.

Whether you’re enhancing web-based games, embedding real-time video editing into your application, or pushing the boundaries of 3D rendering, Wasm stands out as a driving force behind these advancements. To help you, this article will go over what every beginner should know about WebAssembly, what it’s generally used for, and what the future may hold for this promising technology.

The Core of WebAssembly

When you hear WebAssembly, try to think of it as a bridge of sorts — a bridge between the potential of high-performance applications and the open platform of the modern web.

Unlike traditional JavaScript, which is interpreted or JIT-compiled, WebAssembly code is delivered in a low-level binary format, making it both compact in size and swift in execution. This binary format is specifically designed for modern CPUs, ensuring that code runs at near-native speed.

Why Binary?

Wasm’s binary format serves a dual purpose — first off, it means that applications can be much smaller in size, leading to quicker downloads and reduced load times. This increased efficiency is particularly crucial for web apps, where every millisecond of loading time can make a difference to user experience and retention.

Also, because it’s much closer to machine code, the computational tasks are executed faster, bringing applications on the web closer in performance to their native counterparts.

High-Level Languages as Catalysts

With Wasm, devs are no longer restricted to JavaScript alone; they can write complex code in primary programming languages like C, C++, Rust, and more, which is then compiled into Wasm’s binary format, allowing the application to run on the web browser.

For devs of all experience levels, this is absolutely monumental. It means they can now bring performance-heavy applications — like video editing tools or 3D games — directly to the browser without the need for plugins or third-party app stores. On top of that, they can reuse existing codebases — making the transition to the web smoother and more cost-effective.

Security and Sandboxing

WebAssembly’s architecture is engineered to keep security at its core, offering a secure execution environment and vital features like memory safety.

The execution environment operates in a “sandbox,” limiting the potential for security vulnerabilities. This means that even if there’s potentially harmful code, its effects are contained and it can’t harm the user’s system. This is crucial in a threatscape where dangers are manifold — from malware to tax identity theft.

WebAssembly employs a multi-layered security approach to counter cybercriminals who are targeting financial and tax details. By executing code in a confined environment, WebAssembly minimizes the risk of unauthorized access to sensitive information — such as your Social Security number or geolocational data. Encryption protocols can be easily implemented in a WebAssembly module, too, further securing the transfer and storage of vital information.

Therefore, businesses and end users can engage in online activities with greater peace of mind, knowing that WebAssembly’s robust security infrastructure is actively working to mitigate the risks associated with online scams and threats.

Diverse Use Cases of WebAssembly

As Wasm continues to carve its niche in programming, examples of how it’s revolutionizing the web are becoming more plentiful by the day. The following use cases illustrate Wasm’s versatility and potential.


The gaming industry is witnessing a transformative phase, with browser-based games no longer being simple or rudimentary. Thanks to WebAssembly, devs can now bring graphics-intensive games — which were previously reserved for dedicated gaming consoles or powerful PCs — directly to web browsers.

Multimedia Applications

Multimedia applications are vast in scope, encompassing video editing, image processing, audio manipulation, and more. WebAssembly facilitates the creation of browser-based tools that closely mirror their desktop counterparts in terms of functionality and performance. Imagine complex tasks like video rendering, real-time audio processing, or even 3D model design, all being executed smoothly within your browser.

Scientific Computing

In fields like biology, physics, and engineering, computational tasks can be heavy and demanding. Simulations, modeling and data processing, which once required dedicated software and hardware, are now being made available on the web. Wasm can handle the computational intensity; making it possible to run, for example, a genetic sequencing algorithm or an aerodynamics simulation directly from a browser.

Augmented Reality (AR) and Virtual Reality (VR)

Thanks to Wasm, AR and VR are expanding beyond gaming. From virtual shopping experiences and interactive educational platforms, to immersive art installations, WebAssembly provides the backbone needed for these applications.

Other Applications

Innovations like the WebAssembly System Interface (WASI) are pushing boundaries, making it feasible for Wasm to run server-side applications. It’s also a great way to improve the performance of web applications, especially custom ones.

Nowadays, plenty of organizations use bespoke solutions for almost every aspect of their workflow. From everyday tools like a custom DOCX editor or image format converter, to complex creations like rendering engines, WebAssembly is a universal solution.

Not only is it secure, which helps protect IP and trade secrets, but it also runs at near-native speeds, which drastically reduces time-wasting during collaborative work sessions. Likewise, there’s also a noticeable increase in resource efficiency in the backend, allowing organizations to better allocate resources, especially computing power.

Then, you also have e-learning platforms — they often incorporate interactive simulations, coding environments, and real-time feedback systems. WebAssembly can power these features, ensuring learners have a seamless and responsive experience, whether they’re experimenting with a physics simulation or practicing coding in an online IDE.

Last but not least, we can’t forget how important real-time data processing and complex mathematical calculations are in financial platforms. WebAssembly allows for the creation of high-speed trading tools, real-time analytics dashboards, and other financial applications directly in the browser, with performance being comparable to more dedicated software.

Drawbacks of WebAssembly

The use cases and benefits of Wasm, although they are plentiful, don’t exist in a vacuum. In order to fully utilize this platform, one must also consider its drawbacks. This is essential in understanding Wasm’s full array of capabilities. With that in mind, think about the following when considering whether to use WebAssembly.

1. Lack of Garbage Collection

In many modern languages — like JavaScript, Java, or Python — garbage collection is an automatic process that frees up memory no longer in use by the application. WebAssembly’s absence of a native garbage collection system creates a complex environment for memory management. This will be a shocking experience at first, especially for younger devs who are used to having this feature automated.

Developers have to explicitly allocate and deallocate memory, which greatly elevates the risk of memory-related issues like leaks or buffer overflows. Moreover, this also imposes limitations on which programming languages can be ported effectively to WebAssembly. So far, the most suitable options include:

  • Rust: It provides excellent memory safety features and has a robust ecosystem around WebAssembly. The Rust compiler can directly target WebAssembly, and there are tools like wasm-bindgen to facilitate smooth interaction between Rust and JavaScript.
  • C/C++: These languages offer fine-grained control over memory and are well-supported by WebAssembly. The Emscripten toolchain allows C/C++ code to be compiled to WebAssembly easily. Many existing codebases written in these languages have been successfully ported to WebAssembly.
  • AssemblyScript: This is a subset of TypeScript that has been tailored for WebAssembly. It provides a familiar syntax for JavaScript and TypeScript developers, while being designed to compile to WebAssembly efficiently.

2. Limited Access to Web APIs

WebAssembly operates in a sandboxed execution environment separate from the JavaScript runtime. As a result, it can’t natively perform operations like DOM manipulations, or fetch data from web APIs.

To do these, it has to go through JavaScript, which creates a bottleneck and adds latency to the operations. This situation is particularly problematic for applications that require real-time interaction with the web environment. For instance, in gaming or interactive simulations where speed and real-time updates are crucial, having to go through a JavaScript bridge can undermine the very performance benefits that WebAssembly aims to offer.

3. Debugging Difficulties

The debugging ecosystem for WebAssembly is far from mature. The tools available are not as advanced as those for other languages, and the debugging process can often be cumbersome.

If a developer is looking to debug the WebAssembly binary directly, the available options are quite limited. Setting breakpoints, watching variables, and other typical debugging activities become tricky. Source maps, which connect your WebAssembly code back to your readable source code, offer some reprieve; but they too are still not perfectly integrated into most debugging tools. This often results in longer and more frustrating development cycles, especially when Docker and Wasm work in unison.

4. Browser Compatibility

While most modern web browsers offer good support for WebAssembly, there’s a significant portion of users on older versions that don’t. This includes Opera Mini, Legacy Microsoft Edge IE 11, and QQ.

Thus, when targeting a broad user base, developers need to write fallback mechanisms — usually in JavaScript. This creates a situation where essentially two versions of the same functionality have to be maintained. This not only increases the initial development time, but also inflates the ongoing maintenance costs. Every new feature or bug fix has to be implemented twice and then tested across multiple versions, which can be resource-intensive.

5. Security Concerns

WebAssembly is designed to execute code securely within a sandboxed environment, but this doesn’t eliminate all security concerns. Since it allows for the execution of low-level code, there’s a potential for new kinds of cyberattacks, such as integer overflows or buffer overflows, which are less common in high-level languages like JavaScript.

These concerns demand rigorous security auditing and often require developers to adopt additional security measures, like data validation and input sanitization, which add more layers of complexity and can be resource-intensive.

6. Complexity

WebAssembly’s low-level architecture provides a high degree of control over the code execution, but it also demands a deep understanding of computer architecture and low-level programming constructs.

Unlike JavaScript or Python, which handle many operations automatically, WebAssembly requires you to manually manage aspects like memory allocation, stack operations, and binary arithmetic. Such intricacies make WebAssembly less approachable for developers without a background in systems programming or computer architecture.

Additionally, the current documentation and educational resources for WebAssembly are not as abundant as for more established languages, making the learning curve steeper. The learning curve is notoriously steep, and it’s an unpleasant experience for webdev newcomers.

7. File Size

Despite its compiled, binary nature, WebAssembly files are not always smaller than their JavaScript equivalents. Especially when using large libraries or frameworks, the WebAssembly file size can become a concern.

This is particularly important for users on mobile devices or slower network connections, where large files can lead to noticeably slower load times. Developers need to consider this trade-off carefully; even though WebAssembly may execute more quickly once loaded, the initial load time could adversely affect the user experience enough to offset this advantage.

8. Ecosystem Maturity

WebAssembly is a relatively new technology, and as such, its ecosystem is not as rich or mature as other programming languages. JavaScript, for example, has a plethora of frameworks, libraries, and tools developed over more than two decades.

In contrast, WebAssembly’s more limited ecosystem often requires developers to build components from scratch, leading to longer development cycles. Furthermore, while community support is growing, the number of experts and available learning resources is currently limited, making problem-solving more challenging.

9. SEO Implications

Search engines are primarily designed to index text-based content like HTML, CSS, and JavaScript. With WebAssembly’s binary format, the standard tools and practices for search engine optimization may not be directly applicable. This requires additional strategies, such as server-side rendering or using JavaScript to dynamically generate SEO-friendly metadata, to ensure that the content is accessible to search engine crawlers.

These extra steps can add a level of complexity that could make WebAssembly less attractive for publicly accessible web projects where SEO is a major concern. Likewise, if WebAssembly is implemented poorly and it slows down the website or causes compatibility issues, this could negatively impact user engagement, and result in SEO teams having to focus on additional tasks and SEO tactics, such as link building, retargeting, and increased outreach efforts. This can be exhausting for the SEO team and have a negative impact on the site’s rankings if not promptly fixed.

Potential Future Evolution of Wasm

As WebAssembly continues to mature and grow in prominence, it is poised to play a pivotal role in the next generation of web and beyond. Here’s a closer look into the potential trajectory of its evolution:

  • Expanding Beyond the Browser: Wasm’s beginnings may have been browser-centric, but its destiny appears universal with advanced projects like WASI (WebAssembly System Interface) being just the tip of the iceberg. The idea of having a universal runtime can revolutionize software distribution, allowing devs to write once and have their applications run anywhere — from browsers and servers to edge devices and even embedded systems.
  • Integration with Emerging Technologies: The dynamic nature of technology ensures that there are always new frontiers to explore. As technologies like AR, VR, Machine Learning, and IoT gain momentum, WebAssembly is positioned to be at the heart of these integrations. We could soon see more intelligent web applications, augmented reality tools, and interconnected devices leveraging the power and efficiency of Wasm.
  • Growing Tooling and Community Support: A robust technology is only as good as its ecosystem. As Wasm gains traction, the developer community surrounding it is thriving, leading to the emergence of more advanced tools, frameworks and libraries.
  • Enhanced Interoperability: While WebAssembly already boasts significant interoperability with JavaScript and other web technologies, the future may hold even more seamless integrations. As the web standards evolve, we may see WebAssembly become even more central to the core of the internet, allowing for richer, more dynamic, and interactive web experiences.

The Web’s Next Frontier

In short, WebAssembly is redefining the benchmarks of what’s possible on the web. For developers, it’s not just another tool in the arsenal, but a transformative technology that opens up avenues previously deemed unattainable.

As it continues to evolve, the lines between native and web applications might be blurred even further, leading to a truly unified and more robust internet in the future.

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TNS owner Insight Partners is an investor in: Pragma, Docker.
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