Exploring the Potential of Building Containers Using Only a Browser

Container technology, due to its open ecosystem, offers developers who understand its mechanics an opportunity to create custom tools. A striking experiment demonstrating the potential of containers was unveiled on May 24, 2026: a demo where container images can be built entirely within a browser using only client-side code.

A Browser-Only Container Builder This experimental demo allows users to perform the following within a browser: - Select a base image - Specify shell scripts to execute during container startup - Export the generated image as a tar file (which can later be loaded into Docker) By accessing the demo page, users can view real-time logs detailing each step of the build process. The mechanism itself is straightforward. A container image is essentially a “collection of files.” These files can be downloaded, extracted, manipulated, and re-compressed directly within the browser. As long as layers can be constructed within the browser’s sandbox, users have the freedom to make modifications as needed. The source code for the demo is publicly available, enabling interested developers to delve into its inner workings. A linked blog post also provides a technical breakdown of the internal structure of container images.

The Value of a “Not Practical” Experiment The author candidly admits that building containers in a browser might primarily be seen as a “gimmick.” Perhaps this is why no one has documented such an approach until now. However, this experiment holds deeper significance as a demonstration of the power of custom container tooling. When we become accustomed to standard tools like “docker build” and related utilities, we can sometimes forget that creating custom tools is even an option. We simply accept the limitations of standard tools and settle for what they offer. The author argues, however, that the advantages of custom tooling can sometimes be too significant to ignore.

The Dramatic Improvements Brought by Custom Tooling The author cites a recent consulting project as a concrete example. Even for container images several GiB (gibibytes) in size, they were able to reduce the image creation time to “just a few seconds” using custom tools. This level of efficiency is nearly impossible to achieve with standard Docker build tools. By designing and developing their own tools, the team gained full control over architecture, optimization strategies, and caching strategies, resulting in a dramatic speed-up.

Understanding the Basics of Containers Unlocks New Options This experiment underscores the importance of understanding how containers work. By grasping the specifications of container images, developers can build tools optimized for their specific challenges without being constrained by existing tools. Of course, there are many scenarios where sticking to standard tools is the best option. However, the key difference lies in making an informed choice — opting for standard tools not because there are no alternatives, but because they are the most appropriate solution for the situation. The author has previously published articles on unconventional approaches, such as building containers without using Dockerfiles or leveraging S3 as a container registry. These examples also stem from a deep understanding of container fundamentals and a willingness to explore beyond standard practices.

Looking Ahead This experimental demo is positioned as a “research prototype” and is not intended for production use. Nevertheless, the fact that container images can be built even in the constrained environment of a browser highlights the flexibility and potential of container technology. For developers, the message is clear: when faced with the limitations of container tools, we have options. Whether it’s learning the basics and building custom solutions or consciously choosing to stick with standard tools, the decision becomes one of informed choice, not ignorance.