The Journey to Build a Web Browser from Scratch

Getting Started

Building a web browser from the ground up is an immense undertaking that requires expertise in a wide range of technical areas. In this article, we will document one developer’s journey as they aim to create their own browser by detailing the key steps and challenges involved.

Choosing a Programming Language

The first major decision was to select a programming language. While many options exist, a language like C++ was chosen for its performance benefits and extensive standard libraries available. This would allow focusing coding efforts on the browser functionality rather than lower-level tasks.

Implementing Networking Capabilities

Networking is fundamental to any web browser. Hypertext Transfer Protocol (HTTP) and Hypertext Transfer Protocol Secure (HTTPS)were implemented to facilitate requests to web servers. This included functions for making GET and POST requests along with handling responses and any errors.

Parsing HTML, CSS and JavaScript

To properly render and interact with modern web content, the browser needs parsers for the core languages of the web - HTML, CSS and JavaScript. HTML was parsed into a document object model (DOM) for further processing. A CSS parser extracted style rules which could then be applied during rendering.

Rendering Web Pages

A renderer takes the DOM and draws content to the screen. This process integrates layout, painting and composition stages. Flexbox and grid concepts were supported for page structure. Common elements like text, images and tables had to be drawn using the operating system’s native widgets and 2D graphics.

Implementing JavaScript

JavaScript brought the biggest complexities. Beyond parsing, an engine was required to execute code and interface with DOM elements. This included aspects like scope chains, variable object handling and the call stack. Interactive elements like click handlers were made functional through JavaScript integration.

Building out the Browser UI

To complete the browsing experience, work was done on the graphical user interface(GUI) using a cross-platform widget toolkit. Key UI components added were the address bar, tabs, menu bar, bookmarking and fullscreen mode. Usability testing helped refine and polish the final product.

Ongoing Challenges and Improvement

While a basic functional browser was achieved, the work is never truly complete. Continuous improvement is needed to support emerging standards and keep performance optimal. Features like WebRTC, WebAssembly, canvas rendering and media playback still required more effort. Optimization through multithreading was also ongoing. The journey to build the perfect browser is endless.

Lessons Learned

This immense endeavor taught valuable programming and computer science lessons. Successfully implementing core browser technologies deepened understanding of subjects like networking protocols, markup languages, parsers, data structures and GUI toolkits. Learning also came from debugging complex rendering bugs and architectural challenges in JavaScript. Overall, it was an extremely educational and rewarding experience despite significant technical hurdles along the way.

Open Source Contributions

To further advance the project, consideration was given to transitioning the codebase to an open source model. This would allow a community to form, with other developers contributing improvements, fixes and new features. It could evolve much more rapidly than being a solo effort. Issues like licensing, code review processes and governance would need addressing to prepare for an open collaboration model.

Industry Comparison and Standards Compliance

How did the custom-built browser compare to industry leaders like Chrome, Firefox and Safari? Compatibility testing was done against Acid3, CSS and JavaScript standards tests. While passing basic checks, it understandably lacked their full-featured offerings and performance. However, the knowledge gained in reimplementing complex browser internals from fundamentals was immensely valuable.

Further Refinements and New Horizons

While the initial goals were achieved, there remains ample room for enhancement. Accessibility, localization, privacy features and continued optimization of memory usage and startup speed are high priorities. New internet capabilities continually emerge as well, inspiring further browser innovation. Overall, the journey has just begun - but great progress was made in learning through this ambitious multi-year endeavor.